Merge pull request #28 from ulyssecarion/master

Overall result: deprecates "skalarProduct" for "scalarProduct".
Add an isWater method to Group; add water names to GroupType

Adds an isWater() method to the Group interface, which is implemented
in HetatomImpl; ChainImpl's static field 'waternames' has been moved to
GroupType.WATERNAMES.

Updates StructureTools, TestAltLocs, and ChainImpl to use the renamed
and relocated field.