Merge branch 'dev' into 'master'

Implement first versions of file browser, text viewer and image viewer

See merge request bohacfr2/apo-sem!1

refactor: mark font char functions constant

feat: add wTahoma 13

feat: add support for font family

feat: add support for larger fonts

feat: support unicode, modify font types so no big changes are needed

feat: add new font with variable width

docs: add code documentation

refactor: move gui elements to gui library

feat: add font utils