Make cjdns.sh do more, suck less

* Loads `/etc/defaults/cjdns` if it exists so I can change config stuff. Apparently this is a debian thing, so where should it look instead?

* Adds an "update" option, which just pulls the latest cjdns from git, rebuilds and restarts

* Fixed issue caused by merging cjdns and cjdroute

* Removed `$LOGTO`, as only basic startup information is dumped to stdout now