Load derived tables through map-reduce

This allows us to make arbitarily large derived slices, which can be
further aggregated for final usage.
Added new derived tables to HMDA LAR
Added key-compression-map into metadata
Fix tests
Merge pull request #88 from cndreisbach/fix-project-data

Fix project data
Merge pull request #87 from cndreisbach/store-compression-map

Store compression map in metadata