- move platformio.ini out of source directory to be more consistent with 'normal' PlatformIO usage
  - facilitates IDE integration
- add related .gitignores

Update git helper scripts, config comments

Fixed USE_CONTROLLER_FAN #define usage

also removed wayward 'address of' ampersand in setTargetHotend and setTargetBed parameters

Fix broken fwretract recovery extruder feedrate

When both lowering and recovery are performed using the same "prepare_move_to_destination()" the extruder recovery feedrate ends up being ignored and, instead, is only capped by either the maximum e-speed or the time it takes to perform the z-lowering. 
Performing the two moves separately from each other ensures a correct recovery feedrate.

Add EXTRAPOLATE_BEYOND_GRID option to bilinear leveling

Shutdown heaters, autotemp on SD Cancel

Compact smart_fill_mesh slightly

Noted in #6550

Further cleanup of UBL

Implement USE_CONTROLLER_FAN as a feature

Keep refreshing LCD if hotend status is on-screen

Fix BLTOUCH_HEATERS_OFF bug