Clouds and a small bug fix :D

The clouds are now inplemented and functional! :D:D:D
I also saw a small bug: the particle systems created by exploding a
blood cell were not going away so I hacked a thing to kill those. There
is probably a much better way to do it though so feel free to expand it.
I tried to put // James Added on everything I added (I didn't put it on
the particle system fix though. Just look for bursts[] and burstTimers[]
and loops using them.