fix Field.evaluate_at() - do not use FEM-specific attributes
fix Field.evaluate_at() - do not use FEM-specific attributes

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