Add cbsasl implementation

Squash the previous cbsasl repository into this one

Change-Id: I01d855193b11ba4ec4af42230f997e11449b27cb
Reviewed-on: http://review.couchbase.org/34634
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>