Support cube non rectangle

[Justinidlerz]

Support cube tile non rectangle when in the last row or column position

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[Justinidlerz]

I signed it!

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[tjgq]

I think this can be expressed more succinctly as

var levelWidth = this._level.width();
var tileWidth = this._level.tileWidth();
return (this.x * tileWidth + 0.5 * this.width()) / levelWidth - 0.5;

which is the same logic as in FlatView.

[tjgq]

Likewise as above.

[tjgq]

We still want to validate that each tile has at most one parent tile in the previous level (i.e., the tile width must be a submultiple of the parent width, and the same for height). Otherwise, CubeTile#parent and CubeTile#children no longer work correctly.

If you're up for it, you can lift this restriction afterwards (but please make it a separate PR, to keep each change small).

[tjgq]

Add

- The tile width (respectively, height) for a level must be a submultiple of the tile width (respectively, height) for the parent level.

per the discussion above.

[tjgq]

You also need to change the CubeTile#neighbors method. Currently, the logic assumes that an edge tile never meets more than one tile in the other face; this is no longer true with residual tiles.

Consider, for example, the non-residual tile at the top left of the down face. This tile meets two different tiles in the left face: the residual tile at the bottom right of the left face, and the non-residual tile immediately to the left.

A similar situation happens with some of the other corners of the cube. A strategy that might work is to have a lookup table indicating whether a particular corner is "special" or not ("special" meaning that a residual tile meets a non-residual one at that corner). Then add the additional tile to the neighbor set in the cases where the corner is "special".

[tjgq]

This is a great addition, but I have some concerns that need to be addressed. Please see my review comments.