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. 
For the maximum height, I don't know if we would want to do some percentage, because it's more of a threshold; for window sizes lower than it, the blockly height is the window height, and for window sizes greater than it, the blockly height is the threshold. So I think it should be hard coded to some extent. (Or, we could just decide to make the blockly window always X% of the height. )