Rewind to Previous Assignment: Add Arrow or Highlight Lix

[SimonN]

Lix 0.10.22

When you rewind to the previous skill assignment during play, Lix should point out which lix will receive the next assignment. Ideas:

1. Draw the assignment arrow even though the assignment hasn't happened yet. Don't re-show this arrow when we play back the assignment.
2. Or draw a hollow assignment arrow. Then draw the regular full arrow when we play back the assignment.

What should happen when we rewind to the physics update in front of several assignments? Probably: Show an arrow for each lix that will receive at least one assignment.