Elevation bonus and some other things...

Gameplay update:

- Elevation bonus implemented. Turrets built on top of tiles with higher elevation get +1 range per elevation level.

- Camera now turns towards the clicked object to make it centered on the screen.

- Some music and sound effects added to the game. All currently buildable objects have their own base sound effect (for turrets it is used when shooting, for buildings its a looping sound) and also have an explosion sound when exploding. I will create a short gameplay video with sounds soon.

- Game end menu updated. It now has 3 columns (Buildings, Turrets and Damage dealt). Yes, I just noticed the wrong translation in the Turrets column... :)