Changed Cheetah exceptions to show all standard error output.

- In case of an unexpected Cheetah related error, collect stdout, stderr
  and backtrace and display them next to the error message
- Remove one obsolete conditional layer according to PR
- Write all available information about an error into results and output
  result on stdout as well as in writing it into the logfile
- Only show stdout/stderr/backtrace if it is available

Changes according to PR.

Only show stdout/stderr/backtrace if it is available.