Also:
- Add additional message IDs to handle partial SMIL imports
- Ensure negative time strings display consistently
- Update Gradle and dependency versions
- Add gradle-wrapper.jar as recommended in Gradle documentation: https://docs.gradle.org/current/userguide/gradle_wrapper.html#sec:adding_wrapper

Also updated Gradle version

Fixes crash when using MediaButton style on pre-v21 devices

Also removed/updated obsolete .idea files

Also includes the following changes/improvements/fixes:
- Increased minimum SDK to 14
- Migrated to androidx
- Improved file browser
- Improves screen size detection (now prefers real size without menus/bars where obtainable)
- Fixed VLC playback of MOV files
- Added Russian and Dutch translations; fixed missing Spanish translation
- Various lint corrections and minor bugfixes