v2.0.0-alpha.4

While this is an alpha release, new servers should use this rather than an older "stable" version.

This release re-introduces the search results feature that shows the playlists each result is
already part of. This requires üWave Core 0.5.0-alpha.8 or higher. In older server versions, the
feature is far too slow to be used.

Features:

• Request related playlists in search queries.

Internal:

• Reimplement media progress bar in JS. (#2140)
• Read HTML from filesystem on each request. If you upgrade the static files for the web client at
  runtime it will no longer cause hash mismatches. You should still restart the web client's web
  server to pick up server-side changes.