Feature changes:
- #238: add "Focus mode". From @webofpies in #262, #268.
- #266: Add backup file download link.
- #237: Show last backup date, add listing. By @sakolkar in #227.
- Improve dictionary UI, use tabs. With @webofpies in #264.
- #5: Support variable number of dictionaries.
- #261: fix rtl language controls for book add, edit, page edit.
- #223: resize text areas horiz and vert.
Back end changes:
- schema, js changes for dictionary tabs.