Add first draft of new fixture implementation

[markstory]

Add an index generator and state reset implementation. This mirrors the approach used in SQL databases where schema is created once at the beginning of a test and then reused across tests. This will require a bit more setup from end users but yields better performance.

I would appreciate any feedback on the naming and class structure as well as any way the 'schema file' approach could be improved upon.

[othercorey]

Might be good to move the classes into a Fixture namespace so their use is clear. StateReset is a pretty generic name for top-level namespace.