Implement Binary String transit type in C++ stack

Implement Binary String transit type in C++ stack

The C stack got a Binary String component here:
https://gerrit.iotivity.org/gerrit/#/c/2337/

This patch implements it in the C++ stack, and validates it in the unit
test.

Note that this patch does NOT do binary-string-array, but this patch
should be able to demonstrate the effort involved.

Change-Id: I2fd6341f3d84539c3ad5450279f1d755ba211fd6
Signed-off-by: Erich Keane <erich.keane@intel.com>
Signed-off-by: Todd Malsbary <todd.malsbary@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/7937
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Tim Kourt <tim.a.kourt@intel.com>
Reviewed-by: Jon A. Cruz <jon@joncruz.org>