[facets] FacetFilterMixIn: add documention for class and generate_form There is also a small refactoring to make the code clearer. An intermediate variable is introduced and the call is reindented to make it clearer. No logic change.

[facet] Add infered type restriction to Filtered result set (closes #1988776) This does not alter the result while allowing more selection option on other variable than the filtered one.

[source] remove uicfg rule for dropped synchronizing attribute