Z_RAISE_BEFORE_HOMING -> MIN_Z_HEIGHT_FOR_HOMING

rebased
corrected spelling
changed to #elif for error

Still with MIN_Z_HEIGHT_FOR_HOMING but con be done with (folder wide) search-replace when we have a better name.

M110 and M29 rework

Drop obsolete test for leading "N"

update example configurations

Add 'ok' output for G29 actually closing the file.
Handle M110 when received without linenumber/checksumm.

update old comments
update or delete deprecated definitions
complement forgotten updates
adjust spacing
some cosmetic changes

Bugfix: G28 was lifting Z-axis multiple times

Add Watchdog timer reset in kill()

Update name of st_get_axis_position_mm in stepper.h

Related to MarlinFirmware/MarlinDev#270

See: https://github.com/Ultimaker/Marlin/pull/7

As suggested by @max-pau in #3073 - #3074

files.

This changes have being discussed at MarlinFirmware/Marlin#2849.

Disallowed the Z_PROBE_OFFSET_RANGE_MAX to be greater than zero.

 - Remove the forced activation of SDSUPPORT, I guess people may use the ZUM
3D board and not the LCD module.
 - Fixed the tab issue within boards.h file.

Added support for BQ ZUM Mega 3D board and stock Hephestos 2 thermistor.

- Defining `SOURCE_CODE_URL` in `Default_Version.h` overrides it
elsewhere. So don’t define it there.
- Also fix up `language.h` so no `#undef` will be needed.

Addressing issue #2767

Apply `constrain`, `NOMORE`, `NOLESS` and `CRITICAL_SECTION` macros
wherever possible.

Fix layout descr. in configuration_store.cpp

Enhanced #3010 - formal Mesh/Manual dependency

Rc bug fix - Fix for issue #2931

Add CORE support to st_get_position_mm (and elsewhere)

Fix Printrboard with LCD (redo)

Interrupt safe serial --- Guard against non-atomic variable changes from interrupt routines