Add a simple script to use the runexecutor as a stand-alone tool.
This gives an easy way to execute an arbitrary command
and limit and measure resources using cgroups.
This can be useful for manual usage as well as within benchmarking
frameworks. The VerifierCloud will adopt this script as well.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14847 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c