The minor fixes of 1.1.1

After fixing the dpi problems in 1.1.0 and one of my friends confirming that you can run the game on Linux, using Wine,  making a dedicated Linux port less of a priority.  I decided to spend some time polishing the code instead and  ended up changing some things:

- Adding full screen mode: Since the position of objects is now calculated, based on the position of other objects, rather than set by a number, the game can now be run in full screen - it does not make things bigger, but rather allows the player to see more of what is in front of them and correctly attaches the ground, player and obstacles to the bottom of the screen.

- Fixing exploits:  This change of position calculation also makes it impossible for players to set dpi in a way that would cause the player sprite to levitate above the obstacles, making the game unlosable. It can still be used to make the game run slower - making it harder to play.