Feature changes:
- #31: Using page break markers ("---") during new book creation only to force page breaks.
- #133: Set "current language" filter (and setting) from home page.
- #14: Allow term image uploads from keyboard or paste from clipboard.
- Add LWT and LingQ themes. From @imamcr in #285.
- Fix touch-drag problem for mobile. From @webofpies in #286.
- Small bug fixes.