Add freature of Scheduled Group Action.

Add freature of Scheduled Group Action.

We provide function of Scheduled Group Action.
It will send some action message
when preset time is expired.

And we need some function about the time.
These function will use for checking time.

Change-Id: Ib42941db257cd481be4ed6b7f1a8c1b28ff3809e
Signed-off-by: HyunJun Kim <hyunjun2.kim@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/436
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>