fix and extend aurianims

[Gilgames32]

• there were a few inconsistencies, like blend passing two animations as the func argument, typos, bad types etc.
• made it so nil can now be passed as an animation without it breaking
• added new nodes
  • conditional: binary blend with a boolean predicate
  • step: binary mix with a boolean predicate
  • switch: similar to switch-case, the animation will be picked from a table based on the key returned by func
  • vanilla: a modified version of gsanimblend's blendvanilla callback, offsets the rotation of the parts passed with the blend scale, its useful when wanting to play blend vanilla and blockbench animations, when it would otherwise be overwritten