- On `DELTA` the `M665 H` option supplants `M206`
- On `DELTA` `NO_WORKSPACE_OFFSETS` only reverts `G92` behavior
- Spawn 4 conditionals based on `NO_WORKSPACE_OFFSETS`
- Optimize coordinate space conversion for `DELTA` workspace
- To keep EEPROM version, retain `home_offset[XYZ]`, just ignore XY

As suggested in
https://github.com/MarlinFirmware/Marlin/issues/5570#issuecomment-283059
065

implemented G-Code M355 into Marlin

This is in advance of moving non-linear bed leveling to the planner
class.

Also improve the documentation of this and related options, and set
EXTRUDE_MINTEMP to 170 everywhere.