Packed data source builder
Add top-N MRR method
Make item selectors use TestUser
Add most-popular item selector
Fix bad cast in item selector
Delay javadoc runs until jars are built
Document metric thread safety
Use a metric to output user recommendations
Use a metric to output predictions.
Clean up unused recommend/predict layouts
Add missing license headers
Fix JavaDoc error
Clean up task ordering
Add type parameters to output metrics