update term evaluation to use var_dict also with try_equations
update term evaluation to use var_dict also with try_equations

- update ProblemDefinition.create_evaluable()

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