Added support for channel selection on login and through URL parameters

Added support for channel selection on login, channels will be remembered from last visit, they are checked with Regex to make sure they are valid. (Multiple channels can be used).

 You may also specify channels through a URL, such as `/login?channels=Trivia,Test`

If `PRESERVE_CHANNELS` is set, the channel selection will show them. If not, it will default to `#Coldstorm` and `#2`

Note that local versions will default to #test and will need to be disabled before testing locally.

There may be 1 bug that I have experienced a few times, that sometimes channels may be opened twice. I'm not sure if this is related to my changes but a more experienced member should review it.