Cleanup: remove code where a Guava implementation exists,
remove implementations of interfaces that are not properly implemented and not used,
fix modifiers to remove most FindBugs warnings with priority high.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@13292 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c