Made AtomCache exception messages slightly more palatable, although they still get caught and rethrown multiple times

git-svn-id: file:///home/svn-repositories/biojava/biojava-live/trunk@10067 7c6358e6-4a41-0410-a743-a5b2a554c398
Refactored RotationAxis & added documentation

git-svn-id: file:///home/svn-repositories/biojava/biojava-live/trunk@10068 7c6358e6-4a41-0410-a743-a5b2a554c398