Fix MODE/ban handling

[luxaritas]

In the code: https://github.com/EteRNAgame/HTML-Chat/blob/dev/src/js/chat.js#L525

MODE has never been handled correctly (my cousin took a look at the code at one point and mentioned that it doesn't account for multiple modes being set at once, both on the same target or for multiple different targets). Also, the usage of finding the ~q flag on the ban mask to determine if the user is not allowed to post is no longer valid since we're using txircd (it has a different syntax for extended bans - [action[:parameter];[neg][matching:]]mask, so that a mute looks like +b m;nick!user@host).

[luxaritas]

Link was to the dev branch, so the code moved. Persistent link: https://github.com/EteRNAgame/HTML-Chat/blob/0bcd61546b4511b178144a83bb615f6607203a6c/src/js/chat.js#L763

[luxaritas]

Also: Currently only the nick is being checked against the ban mask, so host-based bans (e.g., *!*@somehost) essentially kill all clients