Develop options for filtering GMMs

Develop means to filter the GMM list in GMM apps based on whether the GMM is applicable to subduction or crustal environments. Although some string parsing magic could probably be performed on the current GMM web service usage response, it makes sense to have:

• GMMs support a method that returns their applicable TectonicSetting (issue needed for nshmp-lib). See nshmp-lib#234 (closed)
• Then make changes to nshmp-ws response are required. e.g. The GMM metadata should probably have a tectonic setting field for general utility. The groups should probably also have this field; logic in the app would then be able to enable/display [SUBDUCTION] and [ACTIVE_CRUST, STABLE_CRUST, VOLCANIC] alternative groups in the list. See nshmp-ws#69 (closed)

No change to GMM input fields at this point.