improved particle system performance

I tried the new particle system today and noticed, that it runs a bit slow, especially when using the additive mode.
After some profiling and tinkering around I managed to improve the performance a bit.
There is still much room for improvements, but I think it's a solid start.

The examples show the following fps improvements:
```
                         before       |      after
blending           | normal | lighter | normal | additive
Fire               |   46   |    26   |   60   |    40
Smoke              |   48   |    27   |   60   |    56
Fountain           |   16   |     7   |   60   |    38
Fireball           |   23   |    12   |   60   |    57
Rain               |   34   |    18   |   60   |    30
Cannon             |   60   |    60   |   60   |    60
Explosion Radial   |   35   |    16   |   60   |    25
Explosion Directed |   60   |    60   |   60   |    60
Waterfall          |   15   |    10   |   60   |    24
Multiples          |   21   |    14   |   60   |    33
```

The rain and waterfall example look a bit different than before, but I have not looked into the cause yet.

I think the matrix class could be helpful in managing the transformation of the individual particles.
Also I am planning to try a different approach to the additive mode, because it costs too much performance to use the globalCompositionOperation.