Quantifier elimination: (1) run qe-lite before qe, and (2) the result of a tactic is provided as a result of formulas that have to be conjuncted -- implemented this/fixed the bug.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14274 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c