Fix recent regressions, &c.

- fix broken `M421` due to less-than-careful optimization
- add HOME_AFTER_DEACTIVATE define to advanced config so not everyone has to rehome after steppers are deactivated
- misc. cleanups (remove unused label, unused variables)

Fix broken EEPROM save/load

Implement CRC16, develop mesh allocation table

Spindle / Laser support

Update french language

 - Add crc16 utility function
 - Implement CRC16 for config store, remove old checksum, increment layout version
 - Move UBL mesh store/load to MarlinSettings; increment UBL_VERSION
 - Begin to lay out MAT structure, prototype functions, etc.
 - Rename ubl.state.eeprom_storage_slot to .storage_slot
 - Misc. optimization
 - Cleanup/standardize/improve some messages

This is a work in progress!

Separate SWITCHING_NOZZLE and SWITCHING_EXTRUDER

Prevent home_all_axes picking up XYZ parameters from command

Fix undefined DELTA_PROBEABLE_RADIUS for UBL_DELTA

* Fix M48 for Delta's  There was a scope issue: DELTA_PROBEABLE_RADIUS wasn't getting defined.

* Check if the specified G29 command requires homing

Things should be pretty stable for a while.   
But it wouldn't surprise me if the Delta people have a need for a few special commands.

Since we already used 'T' for `G29` Topology Report in the past, and since 'T' is available…

It was missing MSG_FILAMENT_CHANGE_HEAT_2 and MSG_FILAMENT_CHANGE_HEATING_2

* UBL_DELTA post merge cleanup:
   fix fade_height, lost during some previous merge
   fix float cx,cy which are not const
   move repeated z_cxcy calc line inside loop
   style fixes and comment fixes/alignment

* Update ubl_motion.cpp

remove unnecessary parentheses

* Update Conditionals_post.h

Change name of define to more accurate meaning:
UBL_GRANULAR_SEGMENTATION_FOR_CARTESIAN
which is not and should not be the default for cartesians with UBL.

Also clean up ubl_motion.cpp debug info and fix declaration of cx & cy

Updated Basque translation

More constraint on axis_unhomed_error

Updated Basque translation with new strings.

Update the gMax files to display better with Proportional Fonts

Adding the capability to specify ahead of time how much of the validation pattern to print made it so by default G26 only did one circle and no connecting lines.

It is more natural for the unsophisticated user to just do the entire mesh (bed).   We default the repetition count to GRID_MAX_POINTS+1 to insure we get every last one of them!

UltiPanel was enabled, but technically, it is a REPRAP_DISCOUNT_SMART_CONTROLLER
Either configuration works on the machine.  But we want it 'Right'.

Setup the Proportional Font spacing so columns line up nicer on PronterFace and Repetier Host.

Fix prepare_move... for UBL

Bugfix PRINTER_EVENT_LEDS

Fix FWRetract with positive z-moves during retracted state

Wednesday-Thursday cleaning up after