Improve Ressource Type determination on CSW and CKAN harvesters

Both the CKAN as well as the CSW harvesters do contain metadata about the type of ressources that has not yet been used.

This MR:

• Identifies all types of ressources for the CKAN harvester
• Identifies all types of ressources for the harvesters using CSW.

The CSW harvesters are not looking too promising right now, as the information about file type in the distribution info / format field does not appear to transmit meaningful information, as even if it does align with the given linkage resources, it more often than not does carry information that belongs to the datum itself and not the resource.

I would at this point much rather look into some kind of determination of file type by actuallly looking into link target data.