We mark this historic day, when Marlin went to China.

Level Bed in Prepare submenu

- Add “Level Bed” menu item for auto bed leveling
- Hide the option if homing has not been done yet
- Arrange the Prepare submenu more logically (?)
- Add documentation comments, some white-space
- Apply some coding standards here and there
- Move old encoder multiplier debug option to `ultralcd.cpp`

Edited the European part of 'ISO10646_CN.fon' to match the existing fonts.
Added Chinese font to make_fonts.bat
Created 'dogm_font_data_ISO10646_CN.h'
Added Chinese to 'language.h'
Added 'language_cn.h' with some minor edits.
Added Chinese font in 'language_en.h' to not fall back to European font.
Added cn to 'Configuration.h'
Changed WIDTH to LCD_PIXEL_WIDTH and HEIGHT to LCD_PIXEL_HEIGHT to have more descriptive names.

In 'dogm_lcd_implementation.h'
Added Chinese Font
Made 1 pixel more room for the larger Chinese font on the status line.
Changed geometry of the 'select bar' by one pixel.
Changed the way the position for values and postcars are set.

M111 - Debug Level

- Add `M111` as a standard option to set the debug level
- Implement `DEBUG_ECHO` in `process_commands`
- Other debug levels (e.g., `DEBUG_DRYRUN`) need more work

Rename files to move them in the IDE

Fix BEEPER duration

Add a warning for DISABLE_[XYZ] options

Raise Z for M401 and M402

Use millis_t for progress_bar_ms and expire_status_ms

G4 shows status message only if no message is set already

Apply zprobe_zoffset in axis_is_at_home

Add variant for MAX6675 in M104

- Address issue raised in #1961

Remove set-coordinate extension of G28

Max endstopp

Macro steppercpp

Else will throw error:
@:0 B@:0
Error:No thermistors - no temperature
[ERROR] Error:No thermistors - no temperature

when no bed is defined

delete some tabs

Ensure the probe offset will always be included when homing Z.

Include axis parameter to ultralcd's line_to_current