validation: make sure that fvo ids are globally unique

[dasch124]

Theoretically, all fvo elements should have a globally unique xml:id by prefixing them with the document ids. Since this is beyond the current document-internal validation we've implemented so far, we need to add this.

Currently there are some fvo ids where the "document id" part of the fvo id reads "tf_template". https://github.com/search?q=repo%3Awibarab%2Ffeaturedb+xml%3Aid%3D%22ft_template&type=code

[dasch124]

I think you have fixed those, right @VeronikaEngler ?

[VeronikaEngler]

Yes, I fixed this. So unless I overlooked something somewhere all IDs should be globally unique.