tile-names: rename old tile names to new tile names automatically

when loading a saved city file.
MakeTiles: recognize .xml image specifications
MakeTiles: find and use 128x128 versions of tile images
TileImages: more object-oriented tile-drawing code
TileImages: allow having multiple tile image files
MakeTiles: change meaning of offsetY
TileImages: load image file directly into BufferedImage
TileImages: fix bug (shadowed variable) in LoaderContext.getImage()
TileImages: use new tile-drawing method in drawing-area
TileImages: recognize and use "oversized" option in tiles.idx file
graphics: an alternate image of woods

trees are a little smaller and closer together
MakeTiles: prepare to abstract composition functionality
graphics: initial support for making an oversized tile image
MakeTiles: work on supporting oversized tiles in tile image composer
MakeTiles: only create output files if there's something in them
MakeTiles: add srcWidth,srcHeight args to TileImage api
MakeTiles: let TileImageSprite know the destination size
MakeTiles: remove oversizeAmt property of SourceImage
MakeTiles: fix destination sizing in SourceImage.drawTo
MakeTiles: finish support for oversized (overlapping) tiles