Add Cube::setLimits() which accepts Vector3 for spacing

This adds a new Cube::setLimits() method to accept a Vector3
for the spacing instead of a single double. This allows cubes
to having different spacing values in each dimension.

Change-Id: Iaab9ef0c186b02a3ef60986c35200c7a37bf7c3a
Merge topic 'cube-spacing' into master

03a45a2f Add Cube::setLimits() which accepts Vector3 for spacing