Features: * Download attachments to cache folder (#181) * Regularly delete attachments for deleted notifications (#142) * Translations to different languages (#188, thanks to @StoyanDimitrov for initiating things) Bugs: * IllegalStateException: Failed to build unique file (#177, thanks to @Fallenbagel for reporting) * SQLiteConstraintException: Crash during UP registration (#185) * Refresh preferences screen after settings import (#183, thanks to @cmeis for reporting) Translations: * English language improvements (thanks to @comradekingu) * Bulgarian (thanks to @StoyanDimitrov) * Dutch (incomplete, thanks to @diony](https://hosted.weblate.org/user/diony)) * Chinese (incomplete, thanks to @poi) * French (incomplete, thanks to @Kusoneko) * German (thanks to @cmeis) * Italian (thanks to @theTranslator) * Norwegian (incomplete, thanks to @comradekingu) * Portuguese (Brazil, thanks to @LW) * Spanish (thanks to @rogeliodh) * Turkish (thanks to @ersen) Thanks: * Many thanks to @cmeis, @Fallenbagel, @J117 and @rogeliodh for input on the new attachment logic, and for testing the release