refactored APRON cpa so that it uses the variabletracking precision, like the octagon cpa and the value analysis cpa

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/branches/VariableTrackingPrecisionRefactoring@13452 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c