Scroll blockly

@kadst43 Allows scrolling vertically in the blockly interface, and for screens shorter than the default blockly height, makes the interface the same height as the window.

EDIT: Trouble with the height changing is that, if a user opens the app in a smaller screen, then resizes to a larger screen, the interface will stay the same shorter height. 
@ajiraffe It doesn't have to be a threshold. That's what I was getting at. Even then, we could define `max-height` and `min-height` in CSS and then calculate using a percentage for anything in between. CSS would be the best place to hard-code things like this.