provide more overloads for counter.

Change-Id: I4344504a49682fd070c98da664b5a00fb98a40f6
Reviewed-on: http://review.couchbase.org/40564
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>