SOLR schema: convert license to a docValues field for faster faceting

[Bomme]

Description
Change the type of license to string similar to other fields to mark docValues as true. This should help speed up faceting of search results.

The fieldType definition looks like this:
<fieldType name=“string” class=“solr.StrField” sortMissingLast=“true” docValues=“true”/>

Deployment steps:
Re-indexing required!

[ffont]

This is nice, thanks @Bomme !
Did you check if there are other fields used in faceting that might need similar treatment?

Also in beta search features we do faceting with dynamic fields as well, and I wonder how this would be affecting faceting performance. We'll have to investigate these issues before making some of these extra facets public.

[ffont]

Thanks for the PR @Bomme !
I added an extra change to make the "free cultural works" filter work with the now case sensitive license field. Now this should be ready to merge when Solr is reindexed :)