Merge branch 'dev' into 'master'

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

See merge request bohacfr2/apo-sem!1

feat: use dialog for errors

feat: add get file local path so it can be executed

feat: implement basic directory browser window

refactor: make fileaccess state from union

refactor: do not use dynamic allocation where not needed

feat: add directory list

fix: some file access function types

refactor: fix inconsistency in file access function definitions

feat: add structure for dynamic file access