[Engine-Slick2D] Fixed Sprite offsets
[Engine-libGDX] Fixed offset values of font rendering
[Client] Reduced required object allocations for light calculation
[Engine-libGDX] Using vertex buffer objects to render (slight performance improvement)

This change applies to the sprite batch that is rendering all the graphics. Due to the high amount of texture switches this improves the rendering speed
[Engine-libGDX] Activates texture mipmapping

As all textures that get resized are usually reduced in size, the mip mapping of the textures improves the rendering performance. How ever it takes longer to load the textures and they use more graphic resources.