Manual bed leveling menu fixes.

Homing fixes

lcdDrawUpdate = 2 helped a lot!

- Prevent `Z_SAFE_HOMING` from homing Z twice in some cases
- Allow `G28` with XYZ values of 0 to explicitly set the position
- Don’t add `home_offset` when setting XYZ explicitly in `G28`
- Add `code_has_value` function to check for the presence of a numeric
value (could just test for space or nul to allow other types of values)

Fix doubled lcd_quick_feedback

- MENU_ITEM causes lcd_quick_feedback to be called, so only those calls
to `lcd_goto_menu` outside of the `MENU_ITEM` macro need to set the
`feedback` flag when calling `lcd_goto_menu`.

machine name for hephestos too

Apply CUSTOM_MACHINE_NAME to configs

- Replace “Mendel” with “RepRap”

Latest upstream commits

Break out prevent_dangerous_extrude feature

- In GCodes.md

- It’s inline here, but could be a macro and duplicated for
`planner.cpp`

Fix moves for DELTA for MANUAL_BED_LEVELING

Latest upstream commits

Created a new board to make using RAMPS as a CNC machine controller
easier. It maps pin 8 to the spindle and pin 9 to the controller fan.

- Use `line_to_current` in place of `plan_buffer_line`

+ update in documentation

Made encoderPosition and quick_feedback dependant on NEWPANEL

Cold extrude

Z Probe inverting not present in example configs, causes error

where the hardware is available.
Fix for #1873

Latest upstream commits

Catch dangerous extrude before trying several

Added sanity check for MESH_NUM_X_POINTS and MESH_NUM_Y_POINTS

Moved the definitions of the LCD_STR_* to Conditionals.h

Latest upstream commits

Remove Contrast Menu for device U8GLIB_ST7920

The line const bool Z_PROBE_ENDSTOP_INVERTING = false; // set to true to
invert the logic of the endstop is in the main configuration.h but
wasn't present in the example configuration.h's. Causes a compiling
error with Z Probe enabled. Just added it to all the configs. :)

Thank you @Nprod!