[Feature]Ban offline player in Webui

[mengwei1]

I am a server host, when player from my server reports cheaters to me i cant always respond immediately. Once the cheaters go offline, it is quite difficult to ban them.
I will be very grateful to see that host can ban offline cheater by inputing their steam magic number in the web ui

[TLeonardUK]

I'm working on some general anti-cheat support at the moment, which should help allieviate this.