Channel Access revocation - coverage with differrent SGW versions

Need to allow a new replication version to be specified in order to allow the changing of the 'deleted' flag type as part of the Channel Revocation work.
This will involve:

• Extending go-blip to accept multiple WebSocketSubProtocol values and use inside Context.WebSocketHandshake to match on any
  https://github.com/couchbase/go-blip/issues/27
• Pass values down values from SG inside h.handleBLIPSync 

For 'Needs Functional Test' Sridevi Saragadam :

Following this build we need to:

• Ensure CBL 2.x works properly and can continue replicating to a SGW 3.0 

• Ensure that ISGR replications between 2.8 and 3.0 continue to work as expected this would include both:
      - 2.8 as passive and 3.0 active
      - 3.0 as passive and 2.8 active