Moved all event related types to a new Event folder.
Moved Settings classes to the Configuration folder.
Moved Exceptions to the root namespace.
refactored authentication and added plain and scram sasl authenticators.
added test helpers and MongoDBX509AuthenticatorTests.
added more thorough authentication tests.
refactored and added PlainAuthenticator and ScramSha1Authenticator tests.
cleanup after rebase. Also added more ScramSha1Authenticator tests.