Implement a Live Data Solr source

It would be useful to have a Solr-based live data source, to be able to find and list documents using solr in a Live Data table.

The Solr source could also support an extra "search query" parameter in addition to the regular column filters (note: it would be extra nice to be able to extend this to support CQL queries as well).

It remains to be seen if we would use Solr just for the query (filtering + sorting) or if we would also get the actual data to display from Solr. The latter would make sense for speed while loading actual documents could have the advantage that it would be much easier to re-use the existing LiveTable code to get column metadata.