Remove MOTHERBOARD from "due" entry

Also reformat and document

platformio.ini

 #
-# Project Configuration File
+# Marlin Firmware
+# PlatformIO Configuration File
+#
+# For detailed documentation with EXAMPLES:
 #
-# A detailed documentation with the EXAMPLES is located here:
 # http://docs.platformio.org/en/latest/projectconf.html
 #
 
-# A sign `#` at the beginning of the line indicates a comment
-# Comment lines are ignored.
-
 # Automatic targets - enable auto-uploading
 # targets = upload
 
@@ -27,115 +26,167 @@ lib_deps =
   https://github.com/trinamic/TMC26XStepper.git
   https://github.com/adafruit/Adafruit_NeoPixel.git
   https://github.com/ameyer/Arduino-L6470.git
-default_src_filter = +<*> -<src/config/examples>
 
+default_src_filter = +<src/*> -<src/config>
+
+#################################
+#                               #
+#   Unique Core Architectures   #
+#                               #
+#  Add a new "env" below if no  #
+# entry has values suitable to  #
+#   build for a given board.    #
+#                               #
+#################################
+
+#
+# ATmega2560
+#
 [env:megaatmega2560]
-platform = atmelavr
-framework = arduino
-board = megaatmega2560
+platform    = atmelavr
+framework   = arduino
+board       = megaatmega2560
 build_flags = -I $BUILDSRC_DIR
 board_f_cpu = 16000000L
-lib_deps = ${common.lib_deps}
-src_filter = ${common.default_src_filter}
+lib_deps    = ${common.lib_deps}
+src_filter  = ${common.default_src_filter}
 
+#
+# ATmega1280
+#
 [env:megaatmega1280]
-platform = atmelavr
-framework = arduino
-board = megaatmega1280
+platform    = atmelavr
+framework   = arduino
+board       = megaatmega1280
 build_flags = -I $BUILDSRC_DIR
 board_f_cpu = 16000000L
-lib_deps = ${common.lib_deps}
-src_filter = ${common.default_src_filter}
+lib_deps    = ${common.lib_deps}
+src_filter  = ${common.default_src_filter}
 
+#
+# PrintrBoard (Teensy++ 2.0)
+#
 [env:printrboard]
-platform = teensy
-framework = arduino
-board = teensy20pp
-build_flags = -I $BUILDSRC_DIR -D MOTHERBOARD=BOARD_PRINTRBOARD
-# Bug in arduino framework does not allow boards running at 20Mhz
-#board_f_cpu = 20000000L
-lib_deps = ${common.lib_deps}
-src_filter = ${common.default_src_filter}
+platform      = teensy
+framework     = arduino
+board         = teensy20pp
+build_flags   = -I $BUILDSRC_DIR -D MOTHERBOARD=BOARD_PRINTRBOARD
+#board_f_cpu  = 20000000L     ; Bug in Arduino framework disallows boards running at 20Mhz
+lib_deps      = ${common.lib_deps}
+src_filter    = ${common.default_src_filter}
 
+#
+# PrintrBoard Rev.F (Teensy++ 2.0)
+#
 [env:printrboard_revf]
-platform = teensy
-framework = arduino
-board = teensy20pp
+platform    = teensy
+framework   = arduino
+board       = teensy20pp
 build_flags = -I $BUILDSRC_DIR -D MOTHERBOARD=BOARD_PRINTRBOARD_REVF
-lib_deps = ${common.lib_deps}
+lib_deps    = ${common.lib_deps}
+src_filter  = ${common.default_src_filter}
 
+#
+# Brainwave Pro (Teensy++ 2.0)
+#
 [env:brainwavepro]
-platform = teensy
-framework = arduino
-board = teensy20pp
+platform    = teensy
+framework   = arduino
+board       = teensy20pp
 build_flags = -I $BUILDSRC_DIR -D MOTHERBOARD=BOARD_BRAINWAVE_PRO
-lib_deps = ${common.lib_deps}
-src_filter = ${common.default_src_filter}
+lib_deps    = ${common.lib_deps}
+src_filter  = ${common.default_src_filter}
 
+#
+# RAMBo
+#
 [env:rambo]
-platform = atmelavr
-framework = arduino
-board = reprap_rambo
+platform    = atmelavr
+framework   = arduino
+board       = reprap_rambo
 build_flags = -I $BUILDSRC_DIR
 board_f_cpu = 16000000L
-lib_deps = ${common.lib_deps}
-src_filter = ${common.default_src_filter}
+lib_deps    = ${common.lib_deps}
+src_filter  = ${common.default_src_filter}
 
+#
+# Anet 1.0 - Melzi clone (ATmega1284p)
+#
 [env:anet10]
-platform = atmelavr
-framework = arduino
-board = sanguino_atmega1284p
+platform     = atmelavr
+framework    = arduino
+board        = sanguino_atmega1284p
 upload_speed = 57600
-lib_deps = ${common.lib_deps}
+lib_deps     = ${common.lib_deps}
+src_filter   = ${common.default_src_filter}
 
+#
+# Sanguinololu (ATmega644p)
+#
 [env:sanguino_atmega644p]
-platform = atmelavr
-framework = arduino
-board = sanguino_atmega644p
-lib_deps = ${common.lib_deps}
+platform   = atmelavr
+framework  = arduino
+board      = sanguino_atmega644p
+lib_deps   = ${common.lib_deps}
+src_filter = ${common.default_src_filter}
 
+#
+# Due (Atmel SAM3X8E ARM Cortex-M3)
+#
+#  - RAMPS4DUE
+#  - RADDS
+#
 [env:DUE]
-platform = atmelsam
-framework = arduino
-board = due
-build_flags = -I $BUILDSRC_DIR -D MOTHERBOARD=BOARD_RAMPS4DUE_EFB
-lib_deps = ${common.lib_deps}
-src_filter = ${common.default_src_filter}
+platform    = atmelsam
+framework   = arduino
+board       = due
+build_flags = -I $BUILDSRC_DIR
+lib_deps    = ${common.lib_deps}
+src_filter  = ${common.default_src_filter}
 
+#
+# Teensy 3.5 / 3.6 (ARM Cortex-M4)
+#
 [env:teensy35]
-platform = teensy
-framework = arduino
-board = teensy35
+platform    = teensy
+framework   = arduino
+board       = teensy35
 build_flags = -I $BUILDSRC_DIR
-lib_deps = ${common.lib_deps}
-lib_ignore = Adafruit NeoPixel
-src_filter = ${common.default_src_filter}
+lib_deps    = ${common.lib_deps}
+lib_ignore  = Adafruit NeoPixel
+src_filter  = ${common.default_src_filter}
 
+#
+# Re-ARM (NXP LPC1768 ARM Cortex-M3)
+#
 [env:Re-ARM]
-platform = nxplpc
-board_f_cpu = 100000000L
-build_flags = !python Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
+platform        = nxplpc
+board_f_cpu     = 100000000L
+build_flags     = !python Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
 src_build_flags = -Wall
-build_unflags = -Wall
-lib_ldf_mode = off
-lib_extra_dirs = frameworks
-lib_deps = U8glib-ARM, CMSIS-LPC1768
-extra_scripts = Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
-
+build_unflags   = -Wall
+lib_ldf_mode    = off
+lib_extra_dirs  = frameworks
+lib_deps        = U8glib-ARM, CMSIS-LPC1768
+extra_scripts   = Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
+src_filter      = ${common.default_src_filter}
 
+#
+# Re-ARM (for debugging and development)
+#
 [env:Re-ARM_debug_and_upload]
 # Segger JLink
-platform = nxplpc
-#framework = mbed
-board = lpc1768
-board_f_cpu = 100000000L
-build_flags = !python Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
-lib_ldf_mode = off
-lib_deps = U8glib-ARM
-src_filter =
-extra_scripts = debug_extra_script.py,  Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
-debug_tool = custom
-debug_server =
+platform      = nxplpc
+#framework    = mbed
+board         = lpc1768
+board_f_cpu   = 100000000L
+build_flags   = !python Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
+lib_ldf_mode  = off
+lib_deps      = U8glib-ARM
+src_filter    = ${common.default_src_filter}
+extra_scripts = debug_extra_script.py, Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
+debug_tool    = custom
+debug_server  =
   C:\Program Files (x86)\SEGGER\JLink_V618d\JLinkGDBServerCL.exe
   -select
   USB