Implements Client Management Endpoints

We already had the R of CRUD, this adds the other 3. The 3 new endpoints require an oauth token with the scope `oauth`. Yo dawg, I heard you like oauth?

@rfk r?
@vladikoff you should take a look and see if there's something I've forgotten that the console will need.

fixes #60 
I realize that the choice of 'oauth' as a scheme and strategy wasn't introduced in this patch, but it seems inaccurate to me. OAuth is the protocol that is provided by this server, not an authentication mechanism for requests. "bearer token" would probably be more accurate to describe what's going on. Changing this is probably out of scope for this PR, but it doesn't sit well with me.