Fixup the webhook script

- made the hook work for posts from github and from stash since they
  send different keys for the ref id of the commit.
- removed the -p from the command line usage of mco, since it's not
  supported in the mco agent.
- added a mco output log
- updated the name of the webrick access log variable in the config
  file so its more clear as to what it does.