* Improve translations - thanks:
  * Allan Nordhøy: Norwegian Bokmål
  * Oğuz Ersen: Turkish
  * 109247019824: Bulgarian
  * J. Lavoie: Italien, French
* Show download progress in background download notification
* Add new settings for controlling the cache behaviour
* Remove the "retry installation" button from InstallActivity because it should no longer be necessary
* Fix bugs, cleanup code
* Integrate Weblate