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: Ie5dcd839d8770d219de1d623d60c23be0133bb1c
Signed-off-by: Harish Kumara Marappa <h.marappa@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/2823
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Madan Lanka <lanka.madan@samsung.com>