Merge branch 'dev' at 1.3.0-alpha.

Major fixes:
  #20: Searching uses independent request for each search result section.
  #24: Clicking search input no longer closes search on some browsers.

Minor fixes:
  Escalate button no longer does anything if song is already next.
  #27: Date in activity list can no longer show "in a few seconds".

Features:
  Can limit number of song transcoding jobs happening at once.
  Can specify duration limit for songs to add.
  Some song-adding errors can be shown to user if "displaytext" is set.
  Server gracefully handles missing config values.