[Closes #60] Streamline and fix Actor world coordinates

[kamranayub]

Closes #60

This is a change that should fix problems we've been having with children and grandchildren drawing correctly but reporting incorrect world coordinates.

Due to this fix, I also uncovered #618 and fixed that issue as well (see #619)

Here is the visual test that confirms that children and grandchildren can be scaled + rotated and report correct world coords:

Proposed Changes:

• Add getWorldPos method off Actor
• Take into account Actor graph when calculating scale and rotation
• Add unit and visual tests to confirm reality

[kamranayub]

This is ready to merge when you are.

[eonarheim]

I added the visual test to the list of visual tests