refactoring of value refinement

the DelegatingRefiner now also delegates to a refiner for the value domain, instead of performing value refinements itself

with this change, refinement for the BDD domain by means of the ValueRefiner is for now no longer supported

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14557 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c