Allow secondary package repositories

[numere-bot]

DESCRIPTION

Describe, what you observe or want to be changed:
Having a central package repository is fine, but only if you want to actually make your code public. There is a good reason to allow secondary and probably private/internal-network package repositories as well for an origanisational context.

Describe, what you expect to happen:
During the course of moving the package repository to GitHub, also think about solutions on how we may have secondary and private package repositories for an organizational context. Implement the best solution for that.

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DEVS' SECTION

ANALYSIS

(Describe, what's the issue and which changes have to be made)

IMPLEMENTATION STEPS

(see also our Wiki for implementation guidelines)

• Implement the necessary changes in a new branch created here on GitHub
• Test your implementation

DOCUMENTATION STEPS

(see also our Wiki for further information)

• Update the changes log
• Add comments to your implementation
• Add Doxygen documentation comments- Create or update the documentation articles (*.NHLP and *.NDB files, if needed)
• Update the language strings (*.NLNG files, if needed)

PULL REQUEST

• Create a pull request for your changes
• Fill out the template
• Assign @numere-org/maintainers as reviewers