bug fix: mouseup for dragging only when marking is active
refactor and redesign:
- move 'immediate' modals out of WordController
- introduce ImmediateController, file includes now qStore
- move random/empty and save into CrosswordController
- WordController is no longer needed, EntryController remains
- modals are now displayed on top of the crossword
- load/save buttons at the bottom of the page
- random/empty buttons directly below the crossword grid