Initial work to drop the risk_calculation table
Added a few missing attributes and fixed the export
Fixed engine_test.py
Updated the engine server
Fixed list_calculations
Updated the field uiapi.oq_job.hazard_calculation_id
Simplified list_calculations
Removed the last reference to .calc_id
Reflected the API change in get_oqparam
Moved in the engine the check for obsolete calculation_mode
Some cleanup and added a comment
Merge pull request #1569 from gem/drop-risk-calculation

Drop risk calculation table
Renamed SourceCollector -> TrtModel
Changed the import of the calc module
Merge branch 'db-migrations' into oq-lite
Renamed examples->nrml_examples
Removed get_calculator_class
Made full use of the CallableDict of calculators