Revert "PointSpriteRenderer vertex buffer does not need to be locked on each frame"

This reverts commit 773611c78dabdace110eab9d5f8b54a0d5af92b2.
Render states are now set in the shader
Modifiers now get the correct time delta for their update frequency
added OpacityInterpolator2, RotationModifier and ScaleInterpolator2
added more particle images and updated sample app