[WIP/RFC] Add group type to search facets.

[Psykar]

This is somewhat of a Request For Comment / WIP.

I'm looking at separating search facets by group type. This appears to be the easiest way, and shouldn't much if any overhead. I can't see an easy way to do the split on the results page unfortunately, but perhaps adding this info to the facet won't be frowned on, even if it's only so the info can be available for extensions / helpers / templates.

Currently I'm doing the display of the group type facets in an extension, manually splitting the organizations facet returned by solr based on the type this PR adds, but it requires hardcoding the group types (by overriding dataset_facets, before_search and the get_facet_items_dict helper)

[kmbn]

We decided to close old pull requests that are not actively worked on so that we can focus our effort and attention on PRs made against the current version of CKAN. A lot has changed in the last several months and many PRs will have gone stale or may now be in conflict with the latest version.

Please note: this isn't a judgement about the quality of your pull request. We just don't have the resources to review older PRs.

If you would like to reopen your PR (and update it if necessary), please do!