First Unfinished implementaion of #869.
Initial commit for impact_funtion_metadata.py
Initial IF API implementations
Add several unit tests.
Metadata in improper format.
API for allowed_subcategories.
API for allowed_data_types.
API for allowed_units.
Metadata for earthquake and categorized IF.
Add Metadata class for all IFs
little pep8.
Use id for units.
Update unit test.
Move add_to_list functions and add test_utilities.
Fix wrong indentation.
Fix wrong indentation in volcano.
Update unit test.
Impact Function Manager and the unit test.
Add ImpactFunctionManager to safe.api
Add allowed_layer_constraints and unit_tests.