engine2:
engine2:

More engine scaffolding for risk calcs. A risk calc can now run
completely, with a fake calculator.


Former-commit-id: dc2671197fe006e67d6c4c81c3e522a3906e6f25
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine