[Suggestion] Proxy server support

[earwigsinyourveins]

Discord is blocked in my country, so Discord API is unreachable to me. It also doesn't seem like Dis4IRC respects Java's network settings and uses direct connection anyway.

[zachbr]

Hello, this is not anything I've ever tried so I wasn't aware we had this issue. I would definitely consider us not respecting the JVM's proxy settings to be a bug.

I'll have to rig something up to test this and follow up.