Merge Branch 'master' Into 'homescreen-ng'

1. Conflicts:
2. src/core/specialkey.h
3. src/declarativeitems/griditem.h
4. src/declarativeitems/scalebackgrounditem.h
5. src/editor/charactersviewdelegate.h
6. src/editor/keyboardlayouteditorview.h
7. src/editor/lessontexthighlighter.h
8. src/editor/resourceeditor.h
9. src/models/learningprogressmodel.h
10. src/models/lessonmodel.h
11. src/undocommands/coursecommands.h
12. src/undocommands/keyboardlayoutcommands.h