Support env MARLIN_LANGS for user select generated language, and update doc; update script to generate dogm_font_data_ISO10646_1.h automatically.

Fix #10390

Fix #10388

…to fit more code on the screen and correct outdated commentary contrasting ABL.

Followup to #10375. This is the appropriate place for any system etc folder additions.

[2.0.x] Filament load/unload add acceleration for Bowden

[2.0.x] Z_PROBE_LOW_POINT to prevent probe/bed damage

See https://github.com/MarlinFirmware/Marlin/issues/10317#issuecomment-379100702

As suggested by @GMagician