Corrected @file tags and restored 'Files' section.

Corrected @file tags and restored 'Files' section.

* Corrected @file tags that were inadvertently broken which left their
  comments falling to the next item to be documented.

* Removed unnecessary '@brief' tags and explicit filenames. The latter are
  only required when the @file is targeting a source other than the one it
  is present in.

* Unified formatting of @file doc comment blocks.

* Added 'Files' section back to generated docs.

Change-Id: I7f3fbc3cecf5a922c9f8a98d673bc91a18be8847
Signed-off-by: Jon A. Cruz <jonc@osg.samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/449
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Erich Keane <erich.keane@intel.com>
Reviewed-by: William Dieter <william.r.dieter@intel.com>
Reviewed-by: Patrick Lankswert <patrick.lankswert@intel.com>