discontinuous: new eval_nodal_coors(), DiscontinuousApproximation class
discontinuous: new eval_nodal_coors(), DiscontinuousApproximation class

- update Approximation.eval_extra_coor()

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