Predict OOM failures

[kripken]

BananaBread in very large maps needs a substantial amount of memory. Perhaps we should check during startup that we can allocate a large typed array as a test for how much memory is available, and fail in a more graceful manner if we must.

[cronos3k]

That sounds like a good concept. Maybe we can just load a simple map with a box or the colos map instead with a message saying sorry you cannot load this big map but this will work. Or in the case of the Zoom map we could load the zoomin, or zoomout map that usees the same artwork but is only 10% of the size.