messages/,osd_types: add messages for Push, PushReply, Pull

Signed-off-by: Samuel Just <sam.just@inktank.com>
OSD: add handlers for MOSDPG(Push|PushReply|Pull)

MOSDPG(Push|PushReply|Pull|SubOp|SubOpReply) need the
same thing checked prior to queueing the op, so they
share a templated handler.

Signed-off-by: Samuel Just <sam.just@inktank.com>
ReplicatedPG: add handlers for MOSDPG(Push|Pull|PushReply)

Signed-off-by: Samuel Just <sam.just@inktank.com>
ReplicatedPG: send compound messages to enlightened peers

Signed-off-by: Samuel Just <sam.just@inktank.com>