Created by: zeffii
this addresses two problems that manifest in sv_update_handler
- suppresses double update upon timeline scrubbing
- allows arrow keys to function as normal (nudging current keyframe)
how? by tracking if the sv_update_handler is being triggered on a different 'current_frame' than the previous trigger. The mechanism is currently a dict, but could be switched out for a scene property,, something like 'scene.sv_current_frame`. If we go with this.
I'll leave this for a while before pushing.