Rename scale to anim_scale

[lukehorvat]

Another small rename I hope you'll consider.

From what I can ascertain, actors may have several different scales in their def files: actor_scale, mesh_scale, bone_scale, and scale. My PR concerns this last one, scale. The current naming is a bit ambiguous and the purpose of it is not clear. At first I thought it might be associated with actor->scale, but no, that's dynamic scaling that is applied via ADD_NEW_ENHANCED_ACTOR.

After digging through the code a bit I can see this scale is only used in 3 places: for scaling the Cal3D animation keyframe translations. So it's an animation scale. For this reason, I'd like to suggest renaming it to anim_scale. It'd be nice to rename the scale elements in the xml files too.

Fun fact:
For animations it's typically best to use the skeleton scale (bone_scale) or you risk the mesh becoming deformed when animating, so I questioned why EL has this separate animation scale in the first place. Looking at the actor def files, I found that big spiders are the only actors with an animation scale that is different from the skeleton scale. Their skeleton is much smaller than the mesh, which results in the mesh becoming a bit deformed when animating. Here's their walking animation slowed down:

spider_scale1.mp4

Increasing the skeleton size to match the mesh results in a much nicer animation and mesh:

spider_scale3.2.mp4

I was going to make a PR removing the redundant animation scale entirely in favor of skeleton scale, but then when I set the animation speed back to normal I saw why the deviation was needed for big spiders – the walking animation simply doesn't look good when the skeleton is properly sized:

spider_walk.mp4

So unfortunately because of spiders the separate animation scale is still needed.

[lukehorvat]

I also found a couple of places where get_actor_scale can be called. Included that in the PR too.