UBL:  Minor improvement to G29 P2

M421:  Add 'adjust closest point' capability

- allow H code value to override probing height
- minor cleanups

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

Better mfpub

"M80 S" to report the state of the PSU pin

* M421 Mesh Point Offset and misc. UBL clean up

Allow M421 to accept an offset as well as absolute value for a specified
mesh point.
And misc. UBL clean up to reduce redundent code.

* Better error checking for M421

* Fix M421 Y index bug

I just noticed....  We've had a Y index bug for who knows how long?

Add proportional font adjustment ratio

- update example configs

G26: Add 0.5mm Z-bump between circles to minimize pattern scraping

G26:  Add 'Repeat' Option

UBL Menu System 1.1

- 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

UBL Cleanup/Bugfix

- Fix bug in ubl_line_to_destination
- Improve/fix output of some ubl.h functions

    /**
     * UBL System submenu
     *
     *  Prepare
     * - Unified Bed Leveling
     *   - Activate UBL
     *   - Deactivate UBL
     *   - Mesh Storage
     *       Memory Slot:
     *       Load Bed Mesh
     *       Save Bed Mesh
     *   - Output Map
     *       Map Type:
     *       Output Bed Mesh Host / Output Bed Mesh CSV
     *   - UBL Tools
     *     - Build Mesh
     *         Build PLA Mesh
     *         Build ABS Mesh
     *       - Build Custom Mesh
     *           Hotend Temp:
     *           Bed Temp:
     *           Build Custom Mesh
     *         Info Screen
     *       - Build Cold Mesh
     *       - Fill-in Mesh
     *           Fill-in Mesh
     *           Smart Fill-in
     *           Manual Fill-in
     *           Info Screen
     *         Continue Bed Mesh
     *         Invalidate All
     *         Invalidate Closest
     *     - Validate Mesh
     *         PLA Mesh Validation
     *         ABS Mesh Validation
     *       - Custom Mesh Validation
     *           Hotend Temp:
     *           Bed Temp:
     *           Validate Mesh
     *         Info Screen
     *     - Edit Mesh
     *         Fine Tune All
     *         Fine Tune Closest
     *       - Adjust Mesh Height
     *           Height Amount:
     *           Adjust Mesh Height
     *         Info Screen
     *     - Mesh Leveling
     *         3-Point Mesh Leveling
     *       - Grid Mesh Leveling
     *           Side points:
     *           Level Mesh
     *         Info Screen
     *   - Output UBL Info
     */

PIO Cleanup

Fix compiler complaint related to M100

Patch spacing, const, .gitignore

Fix M100 compiler warnings, general patches

Automatically define Z_MIN_PROBE_ENDSTOP_INVERTING for BLTouch

Move BLTouch LCD menu from Main to Main/Control

For compatibility with DevIoT, until that can be solved.

Rename software PWM variables for clarity

Cleanup previous implementation of new quiet probing

Saves a few lines of code.

PlatformIO-related changes

Minor patches and cleanup