[Rewrite] Restructure Repository Management

[SimonHoenscheid]

This Ticket describes what the new Repository Management looks like

• ideally backwards compatible
• all repo data from hiera (data in modules)
• clear and easy to understand conditions
• easy to add, update and remove repos

TODO:

• create a list/matrix of supported PHP versions and operating systems #604
• create a list of non-default repos #604
• create logic
• create data
• write code
• write tests
• update documentation
• merge to module_rewrite branch