remove unused filename argument of IntegralMeanValueOperator.__init__()
remove unused filename argument of IntegralMeanValueOperator.__init__()

- update LCBCOperators.add_from_bc()

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