Add support for the interface name in the config file

[glaslos]

Add a new field to the config file for the interface name.
We should by default use eth0. Overwrite if config value is set. Overwrite if the flag is provided.
Change the Makefile commands to use the config file instead of hard-coded interface names.

[tank0nf]

Hi @glaslos ,
I’ve been testing the project and it is really impressing. I’d love to take on this issue and work towards resolving it.
Thank you,
Tank0nf.

[glaslos]

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