Selectors query is now available

examples of querys:

http://localhost:8000/files?type=%D0%92%D1%81%D0%B5_%D0%B2_%D0%BE%D0%B4%D0%BD%D0%BE%D0%BC,%D1%80%D0%B0%D0%B7%D0%B4%D0%B2%D0%B0%D1%82%D1%80%D0%B8&subject=%D0%9E%D0%A1,%D0%91%D0%96%D0%94

http://localhost:8000/files?type=%D0%92%D1%81%D0%B5_%D0%B2_%D0%BE%D0%B4%D0%BD%D0%BE%D0%BC,%D1%80%D0%B0%D0%B7%D0%B4%D0%B2%D0%B0%D1%82%D1%80%D0%B8&subject=%D0%9E%D0%A1&subject=%D0%91%D0%96%D0%94