Additional methods for getting Chain type (protein, nucleic, etc)
Adding @Override and @Deprecated tags where applicable

Most were added automatically using Eclipse
Fix #219

Convert GroupType to an enum.
Merge remote-tracking branch 'biojava/master'

Conflicts:
	biojava3-structure/src/main/java/org/biojava/bio/structure/Chain.java
	biojava3-structure/src/main/java/org/biojava/bio/structure/ChainImpl.java
	biojava3-structure/src/main/java/org/biojava/bio/structure/Compound.java
	biojava3-structure/src/main/java/org/biojava/bio/structure/HetatomImpl.java
	biojava3-structure/src/main/java/org/biojava/bio/structure/StructureImpl.java
Documentation improvements
Merge pull request #221 from sbliven/master

Fix #219: Make GroupType an enum