Normalized the table dmg_state
Restored the collapse_map output type
Removed a commented test
Changed the DmgState class to have a foreign key to RiskCalculation; fixed the export mechanism
Removed a now unneeded order_by
Fixed a few comments and docstring
Merge pull request #1026 from gem/1100371

Changed DmgState to have a foreign key to OqJob, not to Output; also removed the CollapseMap special treatment