tests/calcs/risk/hazard_getters_test:

Fixed a few broken tests for the GroundMotionValuesGetter.
Merge pull request #994 from larsbutler/hazard-getter-test-fixes

Risk "hazard getter" test fixes

[r=micheles]
export/hazard:

Added util function for organizing exported hazard curve results by
GMPE and IMT.
tests/export/hazard_test:

Added test for `_get_end_branch_export_path`.
tests/export/hazard_test:

Fixed a typo in test case class name
export/hazard:

Added missing argment in call to `_get_end_branch_export_path` in hazard
curve export function.
tests/export/hazard_test:

Added missing export test for disaggregation.