Correct an error in lang_de

Update distribution date and readme

There is no way to translate "A-travel" to "A Rückzug". Thats simply
wrong.

It sync with the RC.

The fix is simple. Most changes are because of changed indendation,
bacause of leaving early for wrong tool number

We don't have to  avoid German "Umlaute" any more.

General cleanup around high level move functions

- Use new `DEBUG_POS` macro for `DELTA` debug
- Neaten up `prepare_move` a smidgen
- Remove an old commented `prepare_move()` line

Report current position to host after M206 / M428

Renamed stopwatch::status to stopwatch::state

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