A simple sliding-window 2D array datastructure, designed for cheap movement of the window of active elements.
Exposes the following to Lua:
 - constructor(width, height, resolution)
 - ::move(dx, dy)
 - ::get(x, y)
 - ::set(x, y, val)
Notes:
 - Currently not generic, but that should be easy once it's necessary
 - All x/y/dx/dy values are given in terms of the world coordinate space
 - Indexing locations outside of the current window area gives you the default value, and any input ot such a spot is ignored.

See #165
Merge pull request #193 from Revolutionary-Games/165-rolling-grid

A simple sliding-window 2D array datastructure, designed for cheap movement of the window of active elements.