k1 flappy levels

(1) Add k1 flappy levels
(2) Instead of specifying a position in levels.js and only using blockArrangement when loading code that someone else shared, we should just always use blockArrangement.  Added some logic there to change the row size for flappy blocks, and also to make it so that the enter obstacle block's location depends on the presence of other blocks
(3) For freeplay levels that aren't shareable, have a finish button instead of share button (flappy k1 wants to start by showing the finished game so that students know what they're working towards).