Add support for application/ocf.vnd+ocf discovery payloads.

Add support for application/ocf.vnd+ocf discovery payloads.

- Remove baseURI and add anchor property.
- Plumb content format through to parsing/converting payloads.

Change-Id: I05d2a9263b085dec3683f6345190a4b4574ff2dc
Signed-off-by: Todd Malsbary <todd.malsbary@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/17575
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Dan Mihai <Daniel.Mihai@microsoft.com>