CSHARP-554 - Implemented CopyDatabase on MongoServer

This is a relatively simple update.

Implemented CSHARP-554 - CopyDatabase in MongoServer. Did not include a fromHost parameter for now, as I figured we could add an overload in the future. To do that, we'd need a way to handle authentication on the host server of the original database. I added a test to the MongoServerTests.

Sorry about the previous aborted request - I needed to rebase my repo.