Update CMakeLists.txt

This commit includes checking whether ../data directory (from build directory) and ../../stk-assets directory (from build directory) exists or not. If they don't exist, then it gives error message for the corresponding directory. I have included the code for this on line 320.
Update CMakeLists.txt
added achievement banana lover
added an achievement banana lover
merged code with upstream master
Now IA don't fire a cake if the kart is driving too slow. Also correct some comments.
Merge remote-tracking branch 'remotes/upstrem/master' into skiddingAI
Don't fire a cake if the target kart is driving too slow.
Merge remote-tracking branch 'remotes/upstrem/master' into skiddingAI
A kart is now considered as slow if he is slower than the current kart.
Merge remote-tracking branch 'remotes/upstrem/master' into skiddingAI
Glow: Use blit.
Remove an leftover return.
Avoid an extra blit in bloom.
Debug: display cascade in shadow debug mode
Shadows: Clean shaders.
Increase shadow fidelity.
Dont stick to integer coordinate for CSM.
Remove debug logging
Fix roughness in instanced mesh.