allow token to be passed using another method

[danmarsden]

It would be useful if the token could be passed without using the "authorization" header.

I've recently be testing the use of Zapier and trying to trigger Moodle webservices - the restful webservice type gets us close, but for some reason Zapier appears to modify/remove the "authorization" header when it is passed to Moodle so it doesn't work. the webservice webservice_restjson allows you to pass it via the json params, but if we supported passing the token via the url with an extra slash after the function name that might work as well.