Added APK generation to build scripts

Added APK generation to build scripts

Updated android_api SConscript and Gradle files to generate
the APK of android examples with the existing scons command.
If trying to build examples from android studio, the user might
need to update the default TARGET_ARCH, RELEASE and SECURED flags
in <iotivity>/android/examples/gradle.properties

Updated the gradle versions to 1.3.0 in all gradle files.

Change-Id: Id9da3594ac83a4d27b3b1272a5aef6d893b305f9
Signed-off-by: Rahul Rahul <rahul.rahul@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/3135
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Tim Kourt <tim.a.kourt@intel.com>
Reviewed-by: Patrick Lankswert <patrick.lankswert@intel.com>