Redo of #3268 by @jbrazio

Cleanup, simplification of command dispatcher code

Relax the test for "Heating failed" errors

Formatted multi-line comments

Use SBI macro

Fix typo

Make the Autotune option(s) in the LCD menu optional

Host Keepalive: Reduce frequency of "busy" messages

Update Japanese translation

Fixed backlight for PCF8575.

Fix: current_command_args skips digits at the front

These are salvaged from closed-PR #3216.

Follow the PR #3242.

Closes #3245

Fixed backlight for PCF8575.

Signed-off-by: Christian Inci <chris.pcguy.inci@gmail.com>

Fix distribution date

Updated Mesh Bed Leveling

axis_known_position -> axis_homed

Code cleanup around MOTOR_CURRENT_PWM options

In all these cases we want the axis to be homed. If we could have lost
some steps is secondary.

Reenables homing seperate axis with DISABLE_X / DISABLE_Y true.

copy of 406992f9dd

Also add mbl.z_offset to the EEPROM, bumping the version to V23.

Fix a compiler warning in ultralcd.cpp

Closes #3235. Fix dogm lcd error when FAN_PIN is defined as -1

Further cleanup of comments, partial Doxygen-style

Following up on #3231

Fix spelling

Added GPLv3 header to all Marlin files