db/models:

Added `__iter__()` to UHS class to make serialization easier.
export/hazard:

Added `export_uh_spectra`.
tests/export/hazard_test:

Added to `test_classical_hazard_export` to exercise UHS export.
Merge pull request #1092 from larsbutler/uhs-export

UHS Export

[r=matley] [f=1082312]