Added SeparateResponse class for the RCSResourceObject in RE.

Added SeparateResponse class for the RCSResourceObject in RE.

The class is to support the SLOW response concept of the base.
For it, the RCSRequest now holds its owner resource object.

- how to use

RCSSeparateResponse separateResponse;

...

server->setSetRequestHandler([](const RCSRequest& r, RCSResourceAttributes& attrs){
    // make separate response to set result later
    separateResponse = RCSSeparateResponse(r);

    return RCSSetResponse::separate();
});

...

// the set method will throw an exception when the operation is failed.
separateResponse.set();

Change-Id: I054ee3948d7742b5c45f821f3fec48216915f273
Signed-off-by: coderhyme <jhyo.kim@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/4947
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Madan Lanka <lanka.madan@samsung.com>
Reviewed-by: JungYong KIM <jyong2.kim@samsung.com>
Reviewed-by: Uze Choi <uzchoi@samsung.com>