New plugin: Dataverse

This release contains some technical improvements. An important one is that the API code for accessing the Dataverse has been extracted into a new library: ibis/rdm-dataverse-go-api. This library is then also used for the implementation of the new Dataverse plugin.
The new Dataverse plugin can also be used for copying the metadata from the source dataset to the newly created dataset. Note that for this feature to work, the new dataset needs to be created with this tool using the "Create new dataset" button. This button will become available once that the new version of Dataverse (5.13 or higher) is released. Also, you will need to enable creation of incomplete datasets for your Dataverse. See the Dataverse documentation for instructions showing how to do this.