Add more detailed docstring to matchNodeToStructure function.
Define function matchNodeToNode for checking if groups are identical.

Currently can only check Groups against Groups and LogicOrs against LogicOrs
and assumes that everything else is false (which might not be the case, but it's
much harder checking that.)
A set of unittests for the matchNodeToStructure and matchNodeToNode functions
Added unittest for checking if groups are nonidentical in databaseTest
Add incomplete child testing function matchNodeToChild to rmgpy.data.base
Add work in progress parent-child relationship unittest to databaseTest