Improve or add new DDI-XSLT transformations

[borsna]

Project here:
https://github.com/MetadataTransform/ddi-xslt

Some of the transformations can be run in the browser:
https://metadatatransform.github.io/ddi-xslt/

[nbetancort]

I forked the aforementioned project and created an XSLT for transforming a DataCite 4.x XML record into a DDI Codebook 2.5, according to the CESSDA DDI Codebook 2.5 Profile version 3 (https://cmv.cessda.eu/profiles/cdc/ddi-2.5/3.0.0/profile.xml).

You can see the progress at https://github.com/nbetancort/ddi-xslt/blob/master/transformations/datacite/fromDatacite4_ddi25.xslt. It already works, but it is very simple and may not yet cover all the necessary elements. Once it is complete and tested, I will request its upload to the DDI-XSLT repository.

This may benefit small data producers who want to create harvestable metadata for the CESSDA data catalogue. Please note that DataCite does not provide variable information, so the produced DDI Codebook instances only provide descriptions at the dataset/study level.