Make the push url available on the options so modules can use

There are times where modules might want to do more things to the db on a push. This allows them to at least access the push url via the options object. its prefixed with a _ so options._url. The auth can't be passed (at least without a significant refactor) so the modules may have to prompt the user for a username/pass. Not elegant, but the modules can reuse utils.getAuth()