graphics: high-color water
graphics: make a high-color DIRT tile image
graphics: use a transparent layer to implement wires
graphics: experiment with new forest graphics (work in progress)
graphics: more work on hi-color forest
graphics: experiment with an SVG wire tile
graphics: finish work on high-color forest
graphics: TileSpec class for reading tile specification

and rewrite MakeTiles to use the TileSpec class
TileSpec: change format of tile specification
tiles.dat: include animation information in tile specification