BUG : correct the animation on PAUSE and pingpong effect on speed==0

- for speed == 0, we were still rendering by alterning the pingpong textures. we set pingpong = !pingpong in that case to keep the same texture than before
- we add the "animate" variable condition not to update the particles if in PAUSE mode

And as always, modifying initial values for tests and printed values with displayValues()...