added name to tree builders; refactored out TreeBuilder

...ain/java/gov/usgs/earthquake/nshmp/model/Deserialize.java

...java/gov/usgs/earthquake/nshmp/model/FaultRuptureSet.java

...main/java/gov/usgs/earthquake/nshmp/model/GridLoader.java

.../gov/usgs/earthquake/nshmp/model/InterfaceRuptureSet.java

...ain/java/gov/usgs/earthquake/nshmp/model/ModelLoader.java

src/main/java/gov/usgs/earthquake/nshmp/model/ModelUtil.java

.../java/gov/usgs/earthquake/nshmp/model/ZoneRuptureSet.java

src/main/java/gov/usgs/earthquake/nshmp/tree/LogicGroup.java

src/main/java/gov/usgs/earthquake/nshmp/tree/LogicTree.java

...main/java/gov/usgs/earthquake/nshmp/tree/RegularTree.java

...main/java/gov/usgs/earthquake/nshmp/tree/TreeBuilder.java

...t/java/gov/usgs/earthquake/nshmp/tree/LogicTreeTests.java