add overlay/preview
fix BL-L-or-R-or-LR primitive, add 1 pxl transparent noop.png
rename "overlay" -> "preview", start JS for it
move css to separate files
add connections to (preview) cells
move JS to separate files (step 1)
move JS to separate files (step 2 of 2)
rename noop.png -> 1x1-transparent.png; remove layer.neighbours
add junctions to preview; extract util.js
separate Cell and CellView
add setters for play/connections
extract util/EventEmitter, make Cell and play|connections inherit from it
extract quadrants (fka "corners")
use direction.bitMask instead of hard-coded value attr in direction checkboxes
make preview react on play controls (partial)
fix IE bug: "toString" not appearing in `for...in` loop
fix: is[Vertical|Horizontal]Junction based on (p or n) silicon type and connections to neighbors alone
improve preview's reactions on play controls