Do ref matching on the sender side rather than on receiver

Do ref matching on the sender side rather than on receiver

This makes the receiver always send a full list of valid refs, which
will allow us to do better packs, as well as handle creation of new
refs.  Eventually.  Right now we just moved the matching and enabled it.

So now you can do

	git-send-pack host:path branch1 branch2

to only send branches "branch1" and "branch2".