Suppress Code Analaysis warning on

EmailAddress.DebuggerDisplay
Adding IObservableUserEmailsClient and...

default implementation. Still needs delete method which is skipped
because it's a HTTP DELETE. There's currently nothing in the
ApiConnection to handle this scenario and it's a rather unorthodox thing
to support.
delete.
Unit tests for ObservableUserEmailsClient
Integration tests for ObservableEmailsClient

This only tests the GetAll method at this point. Would like to have
Delete implemented before testing Add so that we can do cleanup.