Created a Transform2dPlug and it's test cases.
Changed getChild() calls to use an index from the first plug rather than by name.
Rebased and added Recursive Child Iterator.
Added inherit argument to Metadata query functions.

This defaults to True (the old behaviour), causing metadata for base classes to be returned if none has been registered for the actual class in question. Passing False causes the lookup to fail if metadata has not been registered for the exact type in question.

Fixes #232.
Renamed Transform2dPlug to Transform2DPlug
Merge pull request #234 from goddardl/Transform2dPlug

Created a Transform2dPlug and it's test cases.
Fixed a typo.