better performance for univariate mvc (less constraints for differentiation)
removed bug (unary constr. removed earlier)
not needed anymore
changes for multivariate mean value contractor
uni-variate mean value contractor on all variables implemented
clearing quantifiers
bound on variable "t" in quantifier now expressed via IsElement-constraint
pruneUnivQuantBound: clear bounds after pruning
bugfix pruneUnivQuantBound
removed some bugs, introduced probably some new.
