Add lcb KV Collections Protocol Plumbing

In support of MadHatter's collections feature, add the necessary changes to HELO with collections support[a], retrieve the list of collections[b], and create commands against a collection.

 It is expected this will be on a separate branch or gerrit topic when done.  Please add a reference on how to build it to the engineering wiki page with summary information, including the build number it was tested against.

a) Couchbase Collections - HELLO
b) Couchbase Collections - Collections Manifest