URNs, Links, Templates, Schema, Defaults

[anneschuth]

In this PR I introduce a few changes to the instrument registry format by changing the example iama.yaml.

• Move to urns (instead of IDs)
• Move to links being lists of objects (instead of strings)
• Move to system card templates to make it clear why answers even appear
• Use 'open_question' instead of 'open question' as a task type
• Remove measures folder (leftover)
• Formatted the yaml file
• Introduced a proper schema and schema validation
• Adds all defaults from MinBZK/python-project-template

[anneschuth]

@GuusjeJuijn I've added a proper schema and schema validation as well

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