discontinuous: fix for zero order approximations
discontinuous: fix for zero order approximations

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