Add rollup (metadata) support.
Fix “it” tests.

We were setting the last modified both in the object at creation and in the database resulting in mismatches.
Delete rollup_map entries when we drop dataset.
Rename rollup lookup method and add one to lookup all rollups.
Copy rollup_map when we are creating working copies.
Pull out TableDropper so we can use it for dropping rollup tables
from the secondary.
Whitespace cleanups per Randy's comments, thanks.
Merge pull request #4 from socrata/marcs/rollups

Add rollup (metadata) support to data-coodinator.  Reviewed by Chi.