Release notes for LensKit 2.0.5

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

This is a minor enhancement release in the 2.0 series.

• Add .o.g.l.indexes to lenskit-data-structures to maintain indexes, replacing the old Index and Indexer classes.

• Clean up some of the evaluator’s logging output.

• Run train-test tasks on the main thread when thread count is 1.