Modifications based on RI comments.

Modifications based on RI comments.

- Add doxygen function comments
- Declared functions that were only used in module as static

Change-Id: Ib183811a163b084a303793479f66465f9ca3f1f5
Signed-off-by: Doug Hudson <douglas.hudson@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/636
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Sachin Agrawal <sachin.agrawal@intel.com>
Reviewed-by: Joseph Morrow <joseph.l.morrow@intel.com>
Reviewed-by: Erich Keane <erich.keane@intel.com>