Updates to schema and fixes for validation issues in schema checker

[FedeMPouzols]

This PR combines the branches from #276 (exotic casacore ref frames) and #280 (more updates and fixes to schema).
Fixes #276, Fixes #280

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This contribution is made under the current ALMA software agreements. 
(c) European Southern Observatory, 2024 
Copyright by ESO (in the framework of the ALMA collaboration)

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