title: Solr how to unite filter query
body: <p>I want to make solr unite my filters results instead of nesting it.
  For instance if I start techproducts example, and add 2 filter query(fq) (cat:connector, cat:music) it founds nothing, but each of this cat has many docs. How can I make solr to search in both of this cat and unite results, can I achive that?</p>