Make location types modular

[DavidKerkmann]

Feature description

In a discussion emerging from #1530 we noticed that it would be beneficial for some research questions to split up some location types into others (Schools -> KiTa/Kindergarden/Primary school/Sec. school/University etc.) and to have the user decide which location types to use.

Additional context

Perhaps this could be performed by exchanging the fixed LocationType enum into a more general structure, similar to AgeGroup.

Checklist

• Attached labels, especially loc:: or model:: labels.
• Linked to project.