Renamed Dragger to BoardDragger for future clarity.
Added panning and zooming.

- setUpZoomOnBoard() hooks up the zooming behavior.
- Gave box backgrounds a faint color so you can tell if you're in a box when you are zoomed in very close.
- Fixed missed Dragger => BoardDragger replacements from last commit.
- Extended explanations and tagged the main <svg> with an id.
- Added mrt smart.json/lock to peg boxadder to the version of meteor it was tested with.