Evaluate sprite terminals

[fabio-t]

Something like this:

https://github.com/Emmsii/roguelikedev-does-the-complete-roguelike-tutorial/blob/master/src/com/mac/rltut/game/screen/game/GameScreen.java

Which one to use (ASCII or sprites) should be choosable with a Function key or via config (depending if I can make it work on the fly).

Initially it should be purely 2d top down square tiles, but we might try to play with rectangular overlapping tiles to make depth.