graphics: add the missing trees1.xml file (and dependency)
TileImages: refactor: move SimpleTileImage to graphics package
MakeTiles: use BufferedImage, to be the same as gui
TileImages: refactor: move AnimatedTile to graphics package
TileImages: refactor: move SwitchTileImage to graphics package
TileImage: cleanup: make SwitchTileImage directly refer to default image

rather than have a useless intermediate Case object
TileImage: refactor: s/readTileImage/readTileImageM

this method is called in the context of the parent tag;
it reads all <image> tags that are children of the current tag
and only returns one of them
TileImages: refactor: ren SourceImage to ScaledSourceImage

to allow a non-scaled version soon
TileImage: refactor: LoaderContext now returns a TileImage-derived class
TileImage: teach MakeTiles module how to use LoaderContext
TileImage: continue to consolidate gui vs MakeTiles classes
TileImage: fix for handling of images inside a switch
TileImage: refactor: make separate TileCondition class

to handle current and all future case conditions
TileImage: implement default switch case as its own case with condition==ALWAYS
TileImage: implement realize() function for applying tile conditional logic
TileImage: refactor: eliminate drawWithContextTo()

users should instead call realize() first, with the desired context,
and then use drawTo() on the result
TileImage: implement realizeAll() for all classes

(untested, though)
TileImageLayer: require both elements to be non-null

simplifies some algorithms
MakeTiles: properly handle <switch> images

(unfortunately, with this update I broke animations)