Clone FormElement objects when they are reused
Add a convenience method to create grids with an {{},{},{},...} list
Use the new convenience grid layout initialization method {{},{},...}
Add a way to specify merged cells when creating a grid using {{},{},...}
Fix a nullptr dereference when modifying a Reference that has no model
Allow multiple models when automatically positioning in PositionalLayout
Make it easier to set the Model's root node
Check if the correct Node type is added to a TypedList

Found a few errors after implementing the check.