Further adjustments to UBL code

Support for TinyBoy 2 3D printer (and its OLED display)

The TB2 is a Indiegogo funded 3d printer. It uses a MKS SMELZI V1.0
main board (based on MELZI, i.e. Sanguinololu). I comes as a complete kit,
including display and panel.
Two variants exists, L10 and L16, with a height of 100 and 160 mm.
The heating function of the provided bed can enabled by soldering a
thermistor and some wires to it.

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

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>

UBL additional cleanup

- Make all `unified_bed_leveling` data/methods static
- Move some UBL-related variables into the class
- Replace `map_[xy]_index_to_bed_location` with `mesh_index_to_[xy]pos`

Make MBL a static class, use lookup for index-to-point conversion

UBL cleanup, optimization

General minor cleanup

Fix makefile errors, cleanup

Show Filament Width on LCD when SD is disabled

Fix delta_angles

Convert feedrate on SCARA from mm/s to deg/s

Incorrect optimizations of data types and ternary operators caused some
issues.

Board A4JP should be SCOOVO_X9H

Use safe_delay to ensure watchdog reset

UBL's maps are cleaner.   And with a 1 value, G29 O 1  will generate a
map suitable to be Cut & Pasted into Excel so a Suface Map can be
generated.

The wait_for_user change totally broke UBL.   But there is stuff wrong
now in the thermal code and/or LCD Panel code.

PWM dithering followup

Fix type conversion issue with echo_command

Adjust bilinear grid in M851

With the the current definition of echo_command I cannot compile RCBugFix (Arduino IDE 1.8.1) with the error "invalid conversion from 'const char*' to 'char*'".  This change resolves that.

Immediate commands take precedence

Enhancement of PWM, with dithering