Enhancements for the Concepts macro

[VojtechStep]

This PR:

• Makes concepts throw an error when a wikidata ID is provided without a label. Fixes #1076
• Uses lowercase wikidata labels in the concept tags, and only capitalizes them when generating links. Fixes #1077
• Disallows newlines in quoted parts of the macro. Fixes #1092
• Correctly finds Agda definitions which have single-quotes in them. Fixes #1075
• Adds "(disambiguation)" to concept names in the database, when a disambiguation is provided