fix: fix for missing xsl import that was being ignored

[at88mph]

Changes

• Import for testsVOResource.xsl-v1_0.xsl declared but doesn't exist. Fetched from legacy rofr.ivoa.net.
• Renamed to better fit with other declarations.
• No longer ignores XSL (or missing checkVOResource.xsl) errors
  • Returned error message has (hopefully) meaningful check to resolve the error

[msdemlei]

I think this does what it should, but I think we should re-think the slient fall-back to skipping the XSL tests. If you're as unsure about the implications as I am, I'd say we should fail hard if resources are missing. A validator that might (for instance) pass a service on a local installation (where the file is missing) and then fails on the RofR itself (where the file is there) is I think more confusion than a clean, hard failure (in particular if we explain how to fix it).

Anyway, let's merge this and worry about the silent fallback later.

[at88mph]

Right, good point. There is no rush for this, and I need to fix some conflicts anyway, so I will resolve to fail with a friendly message in that case.

[at88mph]

Good. I created a separate XsltError to handle this. Transform/XSL errors, or just a missing checkVOResource.xsl will no longer return an empty error array. It was actually happening in two places, so both should be plugged now.