Change beatmap import to use OpenTK's FileDrop event
Fix a few issues with database upgrade
Relies on https://github.com/ppy/osu-framework/pull/1100 being merged for most effectiveness.
Fix issues related to hiding beatmaps
Make ProgressNotification's status and progress thread-safe
Fix issues with deletion
Main fix is avoiding nullrefs being thrown when metadata isn't present on a beatmap (quite a common scenario).
Because we are not sharing a single context, we need to use Update to attach the entity to the local context.
Turns out it can fail if file handles are still open.
Use EF for SQLite interfacing
Remove duplicate reference to opentk package
Nuke it all.
Bonus stage
A factory is supposed to be re-used.
Also hard-disables it for uninteresting log levels, providing a further performance boost.