[IOT-1785] Finish role certs feature

[IOT-1785] Finish role certs feature

Add end-to-end testing of role certificate scenario:
- provision role certs
- test role-based ACLs provisioning and enforcement
- test assertion of role certificates

Fix bugs and add new functions as necessary. Added the ROLE_CERT
usage to distinguish role certs (which can't be used for TLS)
from identity certs. Previously they were both saved as PRIMARY_CERT.
Some small changes to save and retrieve role certificates locally. Add
functionality to assert roles (POST the certs to /oic/sec/roles).

Change-Id: I9080e0ca6b0809608621eb8b23dd4bbbfbbb176c
Signed-off-by: Greg Zaverucha <gregz@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/18219
Reviewed-by: Alex Kelley <alexke@microsoft.com>
Reviewed-by: Dave Thaler <dthaler@microsoft.com>
Reviewed-by: Kevin Kane <kkane@microsoft.com>
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Nathan Heldt-Sheller <nathan.heldt-sheller@intel.com>