bring back IDisposable to the UnitOfWork

[seanalexander]

Used code from "\After" for IDisposable.

Verified the application was still functional.

Verified Performance is still acceptable:

Verified there were no open queries during this test using sp_WhoIsActive.

[vkhorikov]

The Dispose() method should come with a using around UnitOfWork in each command handler, otherwise it'd leak connections too.

[seanalexander]

I'll update that and repost--I re-used the example from what was in \After