UPDATE existing P2P pages

UPDATE existing P2P pages:

e.g. https://docs.couchbase.com/couchbase-lite/current/android/p2psync-websocket.html

(and the 3 pages below). 

Much of this content is shared with Replication pages so may already be covered by those changes mentioned above.

Note that intra device sync is covered in UPDATE existing Intra-device Sync (dbreplica.adoc)