ref receiver for methods

[mrkmarron]

What problem would this feature solve? Please describe and, if possible, provide an example.
Currently method receivers cannot be refs so we need to write:
game = game.makeExplicitMove(0, 0, PlayerMark::x);

Do you have a proposed solution? If so please share it.
Should update parser/typechecker to support ref on methods so we can write:

method ref makeExplicitMove(...);
...
game.makeExplicitMove(0, 0, PlayerMark::x);