paperwork - remove options from app menu

there is no point in making half of the preferences accessible directly from the app menu.
paperwork - add back menu items

- add "scan multiple files" / "reindex all documents" because they were removed from app menu
- add "export" in case "print to file" is not available from desktop environment
- sort items
paperwork - add single scan in progress
paperwork - use 64 px-wide doc thumbnails

before, they were about 40 px-wide
paperwork - add document properties popover
paperwork - minor fixes
paperwork - export mockups to png