* Refactor interface to PdmObjectHandle and PdmFieldHandle
Return objects instead of passing in structures as parameters
* Add nodiscard to several functions
* Remove redundant this->
* Rename to ptrReferencedObjectsByType
Move Add and Delete command features there.
Implement generic Toggle Commands.
Make library an cmake "OBJECT" library to allow "registering by static initialization".
Add the concept of CurrentContextMenuTargetWidget into CmdFeatureManager to support the toggle commands.
Updated test application to use the new commands