function findMovableParentOverlay(oOverlay) {
			if (oOverlay.isMovable()) {
				return oOverlay;
			}
			if (!oOverlay.getParentElementOverlay()) {
				return undefined;
			}
			return findMovableParentOverlay(oOverlay.getParentElementOverlay());
		}
Returns the first parent overlay that is movable
@param {sap.ui.dt.ElementOverlay} oElementOverlay - Overlay being checked
@returns {sap.ui.dt.Overlay} - First parent overlay that is movable or undefined