...by moving `homing_feedrate_mm_s` to PROGMEM.

Fix z_endstop_adj initializer

Show the Leveling system in use on the About Printer screen.

Ref #5139

* 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

One click option to manually build UBL mesh.

* Save up to 94 bytes of RAM on 20x4 LCD Display machines

Moved the custom screen characters out of RAM into Program Memory.  With
SD-Card support and the Progress Bar enabled, this saves 94 bytes of RAM
memory.

This was tested using the example_configurations/FolgerTech-i3-2020
files.  So a couple small changes to those files snuck into this Pull
Request.

Probably...  We can find similar savings in the Graphics LCD code it we
comb through it.   And if so...  That is the place we really need to
save RAM memory!

* Tidy up white space and indentation

fix redefinition errors for redundant_temperature

Fix G29 with 3 point

Initializing extruder/nozzle servo when turning on the printer

General cleanup before release

* 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

Removing redundant_temperature from public section and leaving it in the
private section

Allow DEBUG_GCODE_PARSER when UBL is enabled

General cleanup after recent commits

Gcode.cpp - spaces and parameters