Beginnings of a provider for Azure Table Storage

This code uses the [Azure Storage Client Library](http://msdn.microsoft.com/en-us/library/azure/dn261237.aspx) to provide data for EF.

Includes these features:
- [x] Can create a DbContext that uses ATS.
- [x] DbSets can create, update, and delete entities.

The functional tests require configuration against a real Storage account. See instructions in that project's README for details on setting up the connection string for the tests.

I'm not blocked on this pull request; I'm continuing to work on the TODOs