cubicweb #1467 facets w/ query using subqueries [open]

on pages such as we're unable to compute correctly the filter form since tickets are extracted using a query with subqueries, and so generate a bunch of errors while trying to get vocabulary for each facets.

On such case the vocabulary rql should be generated correctly to work with subqueries (by modifiying subqueries as well to fetch necessary stuff).

done in<not specified>
load left1.000
closed by<not specified>