cubicweb #1615869 rangefacet and start_unfolded [validation pending]

RangeFacets do not comply with the start_unfolded attribute spec. A quick look at the code shows that VocabularyFacet use start_unfolded in their _render() method, but RangeFacets do not.

prioritynormal
typebug
done in3.11.3
load0.100
load left0.000
closed by#a4a115aab086 [facets] make rangefacet comply with start_unfolded (closes #1615869)