updated logic tree toString

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

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

.../java/gov/usgs/earthquake/nshmp/tree/EnumValueBranch.java

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

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

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

...in/java/gov/usgs/earthquake/nshmp/tree/RegularBranch.java

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

...ava/gov/usgs/earthquake/nshmp/tree/StringValueBranch.java