1. Made RCSBLigandsFactory handle describeHet queries. 2. Wrote helper
methods for using ligandInfo and describeHet queries with multiple PDB
Ids. 3. Made a backwards-incompatible change: renamed RCSBLigands.get()
to RCSBLigands.getFromPdbId(). This shouldn't be a problem because the
class is so new and has not yet been included in any stable release; if
it is this commit can be reverted. 4. Fixed example usage in header
comment.
Ran cleanup and fixed comments.