Rename the entities in the endpoint paths from singular after we have
agreed that it matches with API design best practices.
Change-Id: I5bdc086c64c6f93e45a13436b65863fc3e8d864e
This change allows the creation and deletion of api keys via the admin API.
It adds two methods for deletion, one via the name and projectID and the
second one via the serialized apikey directly.
Change-Id: Ida8aa729e716db58c671a901e5f7e39253e89a0d