for global refinement with value analysis: add possibility to sort targets (and targets path) for interpolation

based on (expected) quality of interpolants, target path are sorted,
so that paths with favourable interpolants are interpolated first,
which may result in the fact, that others paths do not have to be
interpolated anymore, because existing interpolants are strong enough 


git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@15198 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c