Set up remoting for add/remove

/to @bajtos 

See https://github.com/strongloop/loopback/issues/226
We use `remove` as an alias for `delete` in other places (e.g. DAO's deleteById = removeById, deleteAll = remove) and there is already `__delete__ + name` provided by `lib/scope.js`. 

This method should use a more distinctive name.

How about `unlink`?