added a block
in between commit for adding a sprite to a block
restyled the tile-at calls
added a 'worldblock' and removed block
added more explenaintion to IGridtraveller
added basic worldblock logic, but did not test it yet
merge result
compile merge result took more effort
previous commit did not realy compile, it now does. Also deleted some crappy comments
this code has an example which draws a block on position