[ui] Bad Shell scrolling behaviour

See video. The shell scrolls (both horizontally and vertically) in funny ways:

• When typing, the input starts scrolling way before it hits the end of the screen area.
• When the shell outputs something, the shell doesn't auto-scroll to the bottom. The user needs to do it manually.

If you want to test with the bash shell, add this to hue-shell.ini. You also need to use the spawning server, `build/env/bin/hue runspawninserver':

[shell]
  [[shelltypes]]
    [[[bash]]]
      nice_name = "Bash (Test only!!!)"
      command = "/bin/bash"
      help = "A shell that does not depend on Hadoop components"