Allow OperationImpl to be used elswhere.

Change-Id: I89818f2a94e8e746c562b5a115602f8d3ccfb8d2
Reviewed-on: http://review.couchbase.org/30447
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>