Fix split and move demos

These (and probably others) were broken by the elevation caching change.
Add classes to use and display hex tiled spheres
Switch Move demo to hex grid
Switch Split demo to hexes
Fix data persistence

Support for tiles without climates, and calling limit() to update the
tile elevation cache.
Fix climate demo

For ETOPO, anyway.
Fix erosion demo
Refactor climate method

Climate simulation previously relied on nested list tile structure,
making it hard to adapt to non-rectangular grids.
Switch Climate demo to hex grid
Refactor erode method

Remove dependency on nested structure.
Switch Erosion demo to hex grid
Switch full planet simulation to hex grid

Selection is broken for now.
Change timing logs

Print the current step being logged before it's finished. Makes it
easier to see what's taking up time when watching logs in real time.