backport stable

[doc] split API/book part of stuff that has been moved in primary view module docstring

[rqlrewrite] if inlined relation has to be moved to a subquery, take care of the object of the relation (closes #1945725) As the object of the relation is moved to the subquery, all variables/relations representing some of its attributes or inlined relations should be moved there as well. This avoid error such as "BadRQLQuery: variable AF should be selected by the subquery" on security insertion.

[views/facets] simple horizontal layout when there are a few facets only (closes #1921709)

[breadcrumbs] keep proper breadcrumbs when creating an entity linked to another by inspecting __linkto (closes #1947476)

[web test] secondary view isn't listed anymore by possible view since it use the class_deprecated metaclass

ensure the test for asource column won't crash on SQLServer (closes #1949621)

[doc] backport primary view documentation into the code, also document [URL]AttributeView

[primary sub views] use entity_call instead of cell_call

[doc] get back baseviews documentation into the code, enhance it and reorganize the module accordingly also properly deprecates SecondaryView as it should have been done a while ago.