Add replication status to bucket JSON
Add replication status to bucket JSON

/pools/default/buckets/$BUCKET now has "replication": <float> where
the float is a number between 0 and 1 representing how "caught up"
replication is from that node to any other node. Currently it's 0.0 if
any of the replicators isn't running, 0.5 if they're running but
there's a backfill in progress, or 1.0 if they're running and no
backfill is in progress.

Change-Id: Ia16af486851e801cc4aae8ab212e40bfd54f68fe
Reviewed-on: http://review.membase.org/3660
Tested-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>
Reviewed-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>

membase/ns_server,ceejatec/ns_server,vzasade/ns_server,mschoch/ns_server,nimishzynga/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,pavel-blagodov/ns_server,daverigby/ns_server,nimishzynga/ns_server,vzasade/ns_server,ceejatec/ns_server,nimishzynga/ns_server,daverigby/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,mschoch/ns_server,membase/ns_server,mschoch/ns_server,nimishzynga/ns_server,membase/ns_server,ceejatec/ns_server,daverigby/ns_server,vzasade/ns_server,pavel-blagodov/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,membase/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,membase/ns_server,vzasade/ns_server,t3rm1n4l/ns_server,membase/ns_server,t3rm1n4l/ns_server,pavel-blagodov/ns_server,ceejatec/ns_server,pavel-blagodov/ns_server,ceejatec/ns_server,daverigby/ns_server,daverigby/ns_server