Change EggCrate -> EggCarton
Clean up EggCrate -> EggCarton change.
Use EggConveyor instead of Ground place-holder.
Remove old ground.js
Add root transform to CANVAS

Add a root transform to the CANVAS context so that all the drawing code
works in the Box2D coordinate system. The transform puts the origin in
the lower-left corner, with y-positive going up. Note that this means
all the images will be upside-down.
Prep for adding flappy door and sluice hinge.
Restructure egg conveyer into separate objects.

Separate the egg conveyer into constituent objects. Add the coop door
with hinge.
Make the sluice a kinematic body.
Add a handle at the end of the sluice.
Add basic mouse handling structure.
Get mouse tracking working.
Begin code to set sluice angle.
Fix sluice geometry so it rotates about its origin.
Rotate the sluice via the mouse.
Merge branch 'basic-game-board'