* Remove `banned_ip_for_download?` config option. This isn't something that usually needs
to be configured.
* Replace the `ipaddress` gem with `ipaddress_2`. The `ipaddress` gem has several methods
we need (`link_local?`, etc) that are only available in master because the gem hasn't had
an official release in several years. `ipaddress_2` is a fork that is more actively
maintained.