export/hazard:
export/hazard:

Refactored metadata handling in hazard curv and hazard curve multi
exporters.


Former-commit-id: 03a068e7731dfb2b033ad451f931a53c812ca5d8 [formerly 03a068e7731dfb2b033ad451f931a53c812ca5d8 [formerly aa6e597165a468d4f00c8d563c4e00a9c3e2bdf4]]
Former-commit-id: e804df578690c35b76fd42cca62450b892692f45
Former-commit-id: 8d7f5b33786789bbc6fcf5d9bbc48c98ba47385b
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine