Trail & Particles Improvements

Hi guys,

First of all, thanks for updating the trail renderer and shuriken, it needed some love

Couple of improvements I wish we could have

Trail Renderer

1. Trail look very weird when seen at "tangent" angle (see screenshot), with alignement View or Local.
   
2. Why not use the default curve editor ? Right now, we can't use presets, I think it's a downgrade compare to the basic curve editor...

Particles System

1. Would it be possible to have events ? Something like:
   OnParticleEmited
   OnParticleDied
   OnParticleCollied
   
   Sometime you want to control particles via scripts, but doing it in the Update is not very optimized, having events would be useful.
   
   
2. Does the Trail module could have a curve for width over lifetime option like trail renderer ?
   
   
3. I'm very happy with the new "Random Color" option for Start Color. the thing is gradient can only have 8 differents colors... I don't know if it is a specific limitation, but maybe we could just have an array of colors for this case and not use the gradient ? Or having two options "Random Color on Gradient" , "Random Color in Array" ?

Thanks