Add script exit status information to rawcmd output.

[fredrik-corneliusson]

In web the exit status of the command is communicated.
Add a json object with information on exit status to last line in the rawoutput response text.

Examples:
for OK:
{"result": "OK", "returncode": 0, "message": "Done"}
for ERROR:
{"result": "ERROR", "returncode": 2, "message": "Script exited with error code: 2"}