Updated formatting of comments for better Doxygen output

Updated formatting of comments for better Doxygen output

Converted some end of line comments on enums and structs in the public API
from "//" to "///<" so that the comments will show up in Doxygen API docs.
Added a few comments where I figured out what the elements were.

Change-Id: I8cad63757b0a8a1f0c0f98dbee5f8e5febf5e3a4
Signed-off-by: William R. Dieter <william.r.dieter@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/866
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Patrick Lankswert <patrick.lankswert@intel.com>