Added an IoTivity 'octypes' header file.

Added an IoTivity 'octypes' header file.

This removes the C++ SDK's documentation dependency on the full C SDK's
API. Now, Doxygen generated documentation will not include the full C
SDK's API in its documentation.

Change-Id: Iaedf8ff1ef832b6f32466f9d978fda703d1f3f53
Signed-off-by: Joseph Morrow <joseph.l.morrow@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/878
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Shilpa Sodani <shilpa.a.sodani@intel.com>
Reviewed-by: Erich Keane <erich.keane@intel.com>