Merge RC => RCBugFix changes since RC5

follow-up to commit 200b2487c2

Update release date in another place

Oops! at least 1.6.0

* Description for RC5
* Hint for deprecated Arduino versions

Patch steps rate comment in trapezoid function

Rework Marlin's versioning system

Cleanup for language files

・Remove abolished strings (MSG_NOZZLE1, MSG_NOZZLE2)
・Remove duplicated strings 
・Arrange the strings in unified order
・Adjust spacing
・Remove some comments in Japanese files(follow-up the PR #3560)

The most part of these changes were salvaged from closed my PR#3550.

Move G29 debug output before matrix.set_to_identity()

Fix a typo in #3586 to fix MBL

Allow Z_SAFE_HOMING to compile without a probe

Define dependencies for Z_SAFE_HOMING if left out

Missing Danish translation

Revert MBL menus to "known" working point

Fix menu redraw for DOGLCD, improve MBL

Reduce PROGMEM usage by TWIBus, stopwatch

Fix G92 setting E twice

Z Safe Homing for all

The `Z_SAFE_HOMING` feature is coupled with probes and not leveling, so
make it available for general use.

General code cleanup, improved naming, etc.