First DwC mapping

This first DwC mapping consists of two files:

1. `obis-to-dwc-mapping`: Mapping the current Divebaord OBIS mapping to DwC, to at least get that data to DwC (data -> dwc)
2. `dwc-mapping`: A review of all DwC terms, to extend the current mapping to a complete DwC mapping (dwc -> data).

For both, a status column is used, with the following statuses:

1. `keep`/`use`: use or keep this term
2. `n/a`: term not applicable for these data
3. `unnecessary`: unnecessary term for these data
4. `move`: move current mapping to other term (= merging terms into one)

I also populated with example values I found, and corrected with stripe through where necessary.

Merge request if you agree with this approach. cc @DimEvil