Add AddNewAsync() methods to lists with AddNew which are using IObservableBindingList

[StefanOssendorf]

IObservableBindingList currently only provides a method object AddNew();. This method internally uses a sync Create to create a new Item for the collection.
This is not usable - and can result in a deadlock - when async is required.

Add new methods to the following types and make sure to pass them down the inheritance chain if necessary (like to BusinessListBase).
IObservableBindingList

• AddNewAsync()

ObservableBindingList

• T AddNewAsync()

ViewModel

• AddNewAsync()

ViewModelBase

• BeginAddNewAsync
• DoAddNewAsync

[rockfordlhotka]

I don't think the viewmodel types will be affected.

The "BindingList" types exist to support Windows Forms. And maybe some WPF apps. All the UI frameworks after WPF do not honor or use the "BindingList" concepts (thankfully).

Also, any changes to the behavior of the "BindingList" types need to be thoroughly tested against Windows Forms data grid controls - at least the ones that are in-the-box.