Added the status trend report and API

- Report supports filtering by date and any one of: sku,
  entitlement name or the management_enabled entitlement
  attribute.
- The database query and general data gathering is performed
  by the ComplianceSnapshotCurator.
- The request is processed by the StatusTrendReport class.
Stuff I knew I'd need as part of the algorithm before code was slapped down vs throw-away stuff necessary for the intermediary steps.