Making simulator build optional through scons command line argument "SIMULATOR".

Making simulator build optional through scons command line argument "SIMULATOR".

simulator module will be built only if scons command passed with SIMULATOR
argument having one of the case insensitive value from "True", "Yes", "Y" and
"1".

Example: scons SIMULATOR=1

Change-Id: I466cadaa8b815bc9bd269c147324ccbb32c907dc
Signed-off-by: Harish Kumara Marappa <h.marappa@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/2813
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Madan Lanka <lanka.madan@samsung.com>