presence: rate a resource higher if it was updated more recently
presence: rate a resource higher if it was updated more recently

I don't understand why we didn't have this before. It means that
gabble_presence_pick_resource_by_caps with a dummy predicate will
return the same resource which is totally what we want.

Signed-off-by: Jonny Lamb <3d1fb3642aaab2ff70e3392a5ab916bf99eed6a3@collabora.co.uk>

mlundblad/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble,mlundblad/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble,mlundblad/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble