Listen on all interfaces

[imsnif]

what now listens on the interface given by the -i flag. The default behaviour should probably be "listen on all interfaces", with the -i flag being an optional override.

Things that are needed to do this:

1. The OS layer (eg. os/linux.rs) needs to be adjusted.
2. The OsInputOutput struct needs to be adjusted to get multiple network interfaces.
3. The UI needs to be adjusted to display the name of the local interface where relevant (mostly in the connections table). Maybe something like <eth0>:12345 => 1.1.1.1:54321 shrug emoji