Add a tap mode

[ravicious]

• Switch/check box for it at the bottom of the screen.
  • Persist selection in local storage.
• Special screen when cell is tapped with tap mode on.
  • A zoom on the cell and its neighbours.
    • We could probably automatically calculate how many neighbours to show so that the cell is at least x wide.
  • Buttons for changing bets.
  • Button for zooming out.
  • Tapping on the focused cell acts like a regular click outside of the tap mode.
  • Tapping on any neighbor zooms out.

[ravicious]

There's a WIP on the tap-mode branch, but the whole thing isn't as usable as I thought it'd be. It could use a zoom in / zoom out animation so that it's easier to figure out what's happening.