Method of configuring NMOSTesting to get a GitHub repo that is not https://github.com/AMWA-TV/

[alabou]

When adding new parameters to nmos-parameter-registers it is required to reference a GitHub repo that is not https://github.com/AMWA-TV/ unless having the proper rights to create a branch on the AMWA repo. This requirement also applies to referencing specs in development that do not currently have an official repo.

It would be nice to have an "url" attribute in addition to the "repo" attribute to specify an URL that is not the default "https://github.com/AMWA-TV/" one.