* [New Feature] I2C position encoder support

I plan to continue improving/cleaning this up, as there areas that need work.

* let the cleanups begin.

* progress

* more progress

* comments, rename files, etc.

* clean

* Cleanups per thinkyhead

* a few more cleanups

* cleanups, bugfixes, etc.

* remove unnecessary passes_test(), additional cleanups/optimizations

* cleanups

* misc.

* Fix up I2CPEM.init() and a few other things.

* organize, fix, rename, etc.

* more optimization

* a few more tweaks

* Remove requirement for LCD when UBL is used.

* fix previous oversights

* further refinement - error messages for P2 & P4

* require R on G26 when not using LCD; default to all points

Addressing issue #6901

When using switching nozzle it should be possible to disable the servo after move. Do it only if you do not need the servo power to keep the position.

* Unify M600 and M125 pause features
* Cleanup per thinkyhead's comments
* Rename filament_change_menu_response to advanced_pause_menu_response
* Include HAS_BED_PROBE in QUIET_PROBING
* Update gMax example file
* is_idle() is out of scope without the braces
* Convert FT-i3-2020 to Advance Pause names...
* Allow pause even if not printing

* Misc. Clean Up

Mostly UBL related clean up.
- But fixed a bug in the thermistortables.
- Made G26 more responsive to user aborts.
- Added sanity checks for older name for UBL_MESH_VALIDATION.
- Made G29 P4 able to edit invalidated mesh points
- Restore a reasonable Fade Height for UBL when creating new state information
- Get UBL's Topology Map to look a little bit better
- Make sure the user doesn't see a blank screen when doing Mesh Editing.

* Huh???   GitHub Desktop screwed up!

* get the planner object in scope

* Fix out of scope z_fade_height

* Travis timed out...

I need a change so I can force a new commit and sync.

Changed UBL_G26_MESH_EDITING to UBL_G26_MESH_VALIDATION
Added UBL_MESH_EDIT_MOVES_Z to prepare for that change (coming next)

Plus some other UBL tweaks.

UBL on Delta's....     Should be close!    Should not affect any Cartesian printer.

- 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

The OLED is driven by an SSD1306, connected to the board via
I2C, the rotary encoder is connected to 3 GPIO pins.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>

`Z_MIN_ENDSTOP_INVERTING` must match `Z_MIN_PROBE_ENDSTOP_INVERTING`
when using `Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN`.
This is easy to overlook.