Merge pull request #265 from pmpowers-usgs/gmm-id-naming-260

src/gov/usgs/earthquake/nshmp/gmm/AtkinsonBoore_2003.java

src/gov/usgs/earthquake/nshmp/gmm/AtkinsonMacias_2009.java

src/gov/usgs/earthquake/nshmp/gmm/BcHydro_2012.java

src/gov/usgs/earthquake/nshmp/gmm/Gmm.java

src/gov/usgs/earthquake/nshmp/gmm/YoungsEtAl_1997.java

src/gov/usgs/earthquake/nshmp/gmm/ZhaoEtAl_2006.java

test/gov/usgs/earthquake/nshmp/gmm/SubInterface.java

test/gov/usgs/earthquake/nshmp/gmm/SubSlab.java

.../gov/usgs/earthquake/nshmp/gmm/data/INTERFACE_results.csv

test/gov/usgs/earthquake/nshmp/gmm/data/SLAB_results.csv