Handle UUIDs

[brian-ruf]

Is your feature request related to a problem? Please describe.
The OSCAL GUI must be setup to handle UUIDs, which NIST is moving to in OSCAL starting with Milestone Release 3.

Describe the solution you'd like
Every field that has a UUID flag is required to be assigned an RFC-4122 v4 compliant UUID. The tool should handle this automatically.

Also, many ID reference fields must now be converted from ID to UUID.

Finally, the mechanism that changes the ID field at the root element must be updated to always assign a UUID. On this last point, it already generated the ID, but the field was NCname, so the value had to be prefixed with "uuid-". Now the "uuid-" must not be present.

Describe alternatives you've considered
There is no option for the requirement. This functionality must exist for proper OSCAL processing. There may be alternatives for achieving the requirement, which will be addressed as the issue is worked.