ViewFactoryProperty: Correct toString in defaultValueFn's preSet
ViewFactoryProperty: Correct toString in defaultValueFn's preSet

This fixes a BuildApp serialization problem.

foam-framework/foam,jlhughes/foam,jacksonic/foam,jacksonic/foam,foam-framework/foam,foam-framework/foam,foam-framework/foam,foam-framework/foam,jlhughes/foam,mdittmer/foam,mdittmer/foam,jlhughes/foam,jacksonic/foam,jacksonic/foam,mdittmer/foam,jlhughes/foam,mdittmer/foam