Automatic selection was to unflexible.

Updated documentation

Updated language files to new logic and documentation.

Updated bdf2u8g.exe

This won’t reduce the string storage in the end, but it makes the
language files smaller. Also removed remaining unused strings.

Add 4th extruder

* Depending on extruder count, will add menu items for ultralcd to edit
individual PID parameters for each extruder
* Added menu items to each language_xx.h
* Builds OK, but recommend testing with typical LCD

This reverts commit 2b9722f387.

To test/enable, uncomment the #define DELTA_CALIBRATION_MENU in Configuration.h

Breaking up languages.h makes it easier to translate. Using language
codes makes it easier to select a language and sets the naming standard.