Add the ability to scale the keyboard editor

[ijprest]

The current editor requires a lot of horizontal space for a 104-key layout. It looks OK on my 1600x1200 monitor, but would probably be cut off on a 720p monitor (1280x720).

[dragon788]

It would also be great if you could chose to move the bottom area to the side if you had a super widescreen, otherwise you have to use the site in portrait mode if editing a tall keyboard layout, or scroll down and up frequently (on a 1080p screen).

[ijprest]

@dragon788: This will happen at some point... see #123. The whole UI needs a re-design, now that it has grown so complicated.