[selectors, facet] make is_instance and other EClassSelector subclass gather entity classes from 'select' and 'filtered_variable' context information. Closes #1796732
This allow for instance to use the filter form on rqlst where the filtered variable is not selected
Document: cubicweb-docTitle: CubicWeb documentationAuthor: LogilabAbstract: Some base documentation for CubicWeb users and developpersSection: Apps/ProgrammingFormat: HTMLIndex: /usr/share/doc/cubicweb-documentation/index.htmlFiles: /usr/share/doc/cubicweb-documentation/*.html