absolute coordinates option

• friendlier API for generating sign TileEntity blocks: see sign.py and maze.py for examples
• replace davef's maze with my own

Allow 1.12.2.

• fix mod info dialog in Minecraft 1.12

• preliminary 1.12 Minecraft support

• improved Block constructor, so Block(list), Block(tuple) and Block(block) all work
• can now compare Block to list or tuple

• fix render.py and some model txt files

• maybe fix issues with losing player access
• update chess.py (delete old _sunfish.py if you have it)
• update render.py for Python3
• add pong.py and board2d.py

Fix mcpi/minecraft.py for multiplayer.

Fix chat post fetch in read-only mode.