[LMP Potorchu] Refactored visualization elements into VisBranch.
[LMP Potorchu] Store the visual pad.
[LMP Potorchu] Working VisBranch dtor.
[LMP Potorchu] Use ximagesink for now.
[LMP Potorchu] Delayed element state change.
[LMP Potorchu] Just reset the branch for the visual effect change.
[LMP Potorchu] Connect to VisWidget::nextVis().