Make the Nuxeo shell accept commands and options in no special order

At the moment the first argument to the nxclient.sh script has to be a command ("interactive" or any other).

There was a previous behavior that was not dependent on the argument order but the following changeset changed it:
http://trac.nuxeo.org/nuxeo/changeset/76%3A2663e2b31f2c/nuxeo_shell/nuxeo-shell-commands-base/src/main/java/org/nuxeo/ecm/shell/CommandLineService.java