Update of the thesauri elements based on the vocab.met.no URLs

[ferrighi]

These changes might require some modification in the near future. Relating to #131 #127 #128 and #116, but also in general to the establishment and use of our own URIs vs. external URIs. But I think it's good to have the full list of elements out to start with. This PR includes:

1. modification and extension of all vocabulary files.
2. addition of collection keywords, contact roles, dataset production status, instrument modes and polarisation modes
3. inclusion of minimal provenance information with prov ontology
4. use of sosa ontology to relate platform and instruments (to be extended if relevant - I need some discussion with the ENVRI ontology group)
5. skos mapping with exactMatch/narrower/broader to known vocabularies (mainly gcmd and nerc/bodc vocabularies)
6. the full vocabulary in one single files (both xml and turtle). This is essential for pulling updates from the vocabulary server in the future (see provide a unique file for thesauri #131 )

Note:
URI will not resolve as vocab.met.no has not a registered DNS yet.

[steingod]

Seems fine to me, quite some work done here. As noted I think we have to extend/modify this soon, but this is a really good starting point.