Added Kotlin support, MultiDex, refactoring.
- Added Kotlin support to the app. Welcome, Kotlin! :)
- Added MultiDex support. We finally hit 64K methods!
- Refactored BaseFragment. Moved EditModeListener and related interfaces to BaseMediaGridFragment for easier extension of Media Grid fragments.
- Removed unnecessary listener setters from MainActivity, we can use onAttach for these.
- Fixes crash and behavior #590 (closed)