API Documentation improvements, especially noticable when viewing doxygen output.
*.kicad_mod omits (at 0 0) for brevity.
eeschema, Pcbnew: fix Bug #1255822 (incorrect position of multiline texts when plotting them)
Pcbnew: footprint library table fixes.

* Replace illegal file system characters when reading legacy libraries to
  prevent FPID parsing errors and allow saving to PRETTY file format.
* Create validator to filter illegal file system characters from footprint
  name text edit controls to prevent issues when saving to PRETTY file format.
* Add missing source file licenses and some minor coding policy fixes.