[Editor] Particle effect editor

A particle effect (3d) editor for the Urho Editor.

- I added some things to ParticleEffect to make it a bit more like Material, so that the editor could use a similar approach for ColorFrames/TextureFrames (GetNumColorFrames / SetNumColorFrames, etc) and Undo/Redo (loading/saving to XMLElement).
- The attributes are 'hard coded' as ParticleEffect isn't Serializable and I didn't think of a better way.
- Includes a few ParticleEffect xml's.
- The PR also contains a few angelscript binding fixes for particles.