fix edit_filename() to use prefix
fix edit_filename() to use prefix

vlukes/sfepy,BubuLK/sfepy,RexFuzzle/sfepy,rc/sfepy,lokik/sfepy,lokik/sfepy,RexFuzzle/sfepy,lokik/sfepy,RexFuzzle/sfepy,BubuLK/sfepy,sfepy/sfepy,vlukes/sfepy,sfepy/sfepy,sfepy/sfepy,RexFuzzle/sfepy,rc/sfepy,BubuLK/sfepy,rc/sfepy,vlukes/sfepy,lokik/sfepy