Fix specifications of exit codes for the Guider launcher

[elfring]

I suggest to correct two places in the Guider launcher script.

• A)

                  echo "[Error] fail to find python"
                  exit

  The bash manual provides the following information.

                … If n is omitted, the exit status is that of the last command executed. …
  

  I doubt that the exit status from a successful execution of an echo command (for an error message) is appropriate here.
  Thus I would prefer to use exit 1 instead.

• B)

  $PYTHON -m guider $*
  
  exit 0

  I would prefer that an erroneous execution of the Guider program call will be indicated by a corresponding error code.
  Would you like to delete the statement “exit 0” then?

[iipeace]

I agree with you :)