Create ISO-to-Aardvark XSLT

[thatbudakguy]

This would be a good thing to have as part of full aardvark support. See related OpenGeoMetadata/metadata-issues#3.

If we do this by updating the existing iso2gbl.xsl, it might be a good chance to resolve some longstanding issues with it:

• Invalid date string in iso2geoBL.xsl #14
• Discrepancy in publisher element between iso2geoBL.xsl and GBL Metadata schema #62
• ISO/FGDC to GeoBlacklight should generate dct_references_s #11 (won't matter anymore with aardvark)

[srappel]

We have one on our fork: https://github.com/UWM-Libraries/GeoCombine/blob/main/lib/xslt/iso2geoBLAardvark.xsl

It's probably got some localization, but might be useful for reference.

[srappel]

I'm finding out that our XSL uses XSL 2.x features that are not supported by Nokogiri. 😞