Switching selected fiducial list should update the currently-visible ROI

[allemangD]

Related to #21. Possibly related to #13.

Steps to reproduce:

1. Open PickAndPaint, select a model.
2. Create a new fiducial list (MarkupsFiducial)
3. Add a point and set a radius.
4. Create a new fiducial list (MarkupsFiducial_1). Desired behavior: the ROI associated with MarkupsFiducial should no longer be visible.
5. Add a point and set a radius.
6. Select the first fiducial list (MarkupsFiducial). Desired behavior: the visible ROI should switch back to the first one.

Instead the visible ROI only switches when a new point is added.

Discovered while investigating #16.