Support for universal repositories

[z0idb3rg]

Is your feature request related to a problem? Please describe.
Tenable SC now provides universal repositories, which can include multiple / different dataFormat. pyTenable doesn't support (e.g. creation of) universal repositories yet.

Describe the solution you'd like
Expand SC funcionality to support creation and use of universal repositories.

Describe alternatives you've considered
update repo_type check and documentation in repositories.py to include 'universal'

Additional context
N/A