* ADD: allow using numbers in "query id" fields;
* FIX: hierarchical filters workflow with additional providers;
* FIX: filters workflow with the products loop widget;
* FIX: hide filters items in the Safari browser;
* FIX: minor bugs;
* UPD: front-end code refactoring;
* ADD: allow to choose additional provider for filters;
* ADD: show empty terms for checkboxes, select, radio and visual filters;