Relocated ambient light contribution
Merge pull request #458 from Davhed/gouraud-fix

Bug fix - Relocated ambient light contribution in GouraudMaterial
Added cleanup for plugins for onDestroy()
Fixed array out of bounds bug

Added index bound checking for AccelerateDecelerateInterpolator.
Merge pull request #460 from AndrewJo/master

Clean up for Plugins during scene destruction
Added destroy() method
Merge pull request #463 from AndrewJo/master

Destroy method in IRendererPlugin