Rewrote client in Angular

TODO: Implement 'signup-response' socket event
TODO: Merge send-private and send in socket interface
TODO: Make messages fade when disappearing
Implemented signup-response and merged send

Implemented signup-response, added login warning messages to the login
modal dialog box, made the dialog hide only if the login/signup was
successful, and merged send-private into send
Added userlist scrollbar, chat filter and logout