fix check for scalePivotTranslate when enableReadAnimatedValues is changed

[pmolodo]

Description (this won't be part of the changelog)

Fix for the setting of scalePivotTranslate in enableReadAnimatedValues - it was checking scalePivot instead of scalePivotTranslate.

Also, scalePivotTranslate / rotatePivotTranslate are vector values, not points.
Also reverted a change to not use, ie, MVector::zero, per Rob's note here:
#112 (review)

Changelog

Fixed

• check for whether scalePivotTranslate needs to be set enableReadAnimatedValues was checking if scalePivot was set, not scalePivotTranslate

Checklist (Please do not remove this line)

• Make sure the Title and Description of the PR make sense and provide sufficient context for your work
• Do any added files have the correct AL Apache Licence Header?
• Are there Doxygen comments in the headers?
• Are any new features, behaviour changes documented in the .md format documentation?
• Have you added, updated tests to cover new features and behaviour changes?
• Have you filled out at least one changelog entry?

[robthebloke]

lgtm