Huge performance increases. Accepting data, rendering the incoming stream
into lines, displaying contents (and scroll back) on the screen have been
decoupled from each other and many are now triggered by timers and run with
far less regualarity than before. This means we can skip tons of unneeded
work.
Sped up the rendering of the scrollback lines to the DOM by combining innerHTML calls.
Send keystrokes for Ctrl+Shift+_ and Ctrl+Up/Down/Left/Right.
More work to let other Ctrl+Shift combinations go through to the application.