New UI translation: Chinese (Simplified Han script)
New feature: note tree now shows note icons

Bugfixes:
- Handle decryption errors without crashing
- Handle sync errors when app is closed without crashing
- Fix crash when editing content without successful sync
- Fix crash when clicking on deleted note in tree
- Fix startup crash on some old Android devices
- Fix self-signed certificate detection on some devices
- Fix crash in note map with broken relations
- Allow FABs to be disabled completely