onDeleteContext(oEvent) {
			var aItems = this.oSelectedContextsModel.getProperty("/selected");
			var oToBeDeleted = oEvent.getParameter("listItem");
			var oNewData = aItems.filter(function(oItem) {
				return oItem.id !== oToBeDeleted.getTitle();
			});
			this.oSelectedContextsModel.setProperty("/selected", oNewData);
			// after deletion put the focus back to the list
			var oList = oEvent.getSource();
			oList.attachEventOnce("updateFinished", oList.focus, oList);
		}
Removes a single selected context.
@param {sap.ui.base.Event} oEvent - Event object