Filters

Moved all code that deals with filters into separate module.

class Filter implements  filter methods. Call of filter method returns FilterItem as a result.
FilterItem represents applied filter, remove or pin methods are attached to this object.
PageObjectModels for Pages with filter features should include Filter class via property as usual.

Updated all tests and all pages to those changes.

All tests passed in Firefox.
Bunch of tests fail in Chrome, but failures are not linked to refactoring of filters.