Use Visitor Pattern for visiting SymbolicValues.
Use a visitor for SymbolicValues in formula creation of satisfiability check in ConstraintCPA.
Since we now have three interfaces for formula creation, create new single interface 'FormulaCreator' for bundling them.




git-svn-id: https://svn.sosy-lab.org/software/cpachecker/branches/symbolic@14769 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c