Moving CouchbaseClient docblocks to the IF and adding @Override.

Since the CouchbaseClient grows out of bounds with the recent
additions, moving the docblocks makes it shorter. Also, this is
where they belong to anyway. Actual refactoring of the code
will follow in separate commits.

Change-Id: I8d9f3a6c64a41b58c9a25df69fc17864acabd6ff
Reviewed-on: http://review.couchbase.org/29541
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>