Set exit code of CPAchecker to "1" if invalid command-line arguments are given.
Also change handling of error messages and exit code to always use System.err and a consistent exit code.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14522 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c