Based on #8565

Example Configuration.h files are not updated yet.   You need to cross
your settings over to the default Configuration.h file in the \Marlin
directory.   (UBL_G26_MESH_VALIDATION enablement has moved to a new
location in the file.)

set_destination_to_current() changed to set_destination_from_current()

set_current_to_destination() changed to set_current_from_destination()

while heating, G26 will continuously spam the heater states instead of printing it out every 5000ms.

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also an issue with ubl_motion.cpp

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Changed to conditional compile for AT90USB issue

* 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

* Change all direct changes of ubl.state.active to
  set_bed_leveling_enabled() which handles apply/unapply
  leveling to maintain current_position consistency.

Fix invalidation of UBL mesh to invalid unreachable
  mesh points as well (delta corners).

Fix UBL_DELTA unapply_leveling logic and when
it gets applied, including fade_height changes.

Add optional M114 D for detailed position information,
disabled from compilation by default (M114_DETAIL).

* UBL_DELTA raw and inline kinematics

* UBL planner fall through fix

* consistent variable names

* Cleanup orphaned code and whitespace changes.
Use _O2.

* compile warnings cleanup

* Remove redundant #ifdef condition

* 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)

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

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!

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

- Split M421 into separate versions for bilinear and ubl
- Fix minor issue in G26

- Allows for specifying number of points to print/validate, using 'R' code like with G29 P4 Rx
- Moved the code for Random to 'M' so we could be consistent with G29 P4
- G26 instructions indenting/cleanup