Graizer GMM

See #123 (closed)

Initial implementation of the Graizer 2018 model. Incomplete. Requires feedback from author.

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

@@ -250,6 +250,13 @@ public enum Gmm {
       SadighEtAl_1997.COEFFS_BC_HI,
       SadighEtAl_1997.CONSTRAINTS),
 
+  /** @see Grazier_2018 */
+  GRAIZER_2018(
+      Graizer_2018.class,
+      Graizer_2018.NAME,
+      Graizer_2018.COEFFS,
+      Graizer_2018.CONSTRAINTS),
+
   /* Subduction Interface and Slab WUS 2008 2014 2018, AK 2007 */
 
   /** @see AtkinsonBoore_2003 */