Made queue name configurable through the application configuration file

Related to #14.
It's a necessary evil that the other configuration values are blank: it's because the values contain security-sensitive information, or because there's no obvious default value. It's still a bother that these values are blank, because it means that in order to ad-hoc test the application, one has to provide values (and then one has to remember to remove the values again before checking in).

The queue name, on the other hand, has a sensible default, and was, until this commit, hard-coded for all to see.