Release 0.5

The Mercurial changelog and the list of closed tickets provide more information on what has happened, including bugs that have been fixed.

• Reworked IndexedPreference, making it an interface that can be backed by indirect implementations in rating snapshots. This seems to be faster. Also added getIndex() method, returning a global index for the preference within a snapshot.
• Adjusted the FunkSVD model builder to use global indices and an array of estimates, making model builds much faster.
• Dropped by-user MAE from MAE evaluator and renamed “MAE.ByRating” in output to “MAE”, as per-user and global MAE are equivalent.
• Moved TaskTimer to lenskit-core so it is available for logging elapsed times in algorithm implementations.