RDF Faceting: facet object queries

[agazzarini]

The plain facet.field, although being the first conjunction step between RDF and Solr capabilities, is quite unuseful; instead in an RDF context it should be useful to have a new kind of field faceting where the objects can be selected by a query on a given field. For example

facet.field.q=p:http://a.b.c#publication_year

So a query, parsed by default with a Solr Query Parser, could identify the objects that define the facet values domain.

[agazzarini]

Work is moreless completed, not yet committed because I want to create a huge test suite for this specific feature.

More details soon in the Wiki