Fixed minor issue where manual 'have' tracks would be unmatched if a local file was deleted.
Added database indices on allalbums/alltracks tables.  Active artist update FLIES throughout the process when starting from scratch.
Fixed minor bug where track numbers were out of order on album page (due to new index)
Added indices on tracks/alltracks/have tables to speed up library sync & improve overall speed of browsing headphones.
Merge remote-tracking branch 'theguardian/master' into develop