Smorin4/edit multiple

[smorin4]

Body of work done to prototype multiple selection within the edit project menu. All changes were made inside the SharedFunctionality.UI project, the majority being in the VisualStudio/NewProject and VisualStudio/NewItem folders. Each of these folders contains its own MainViewModel.cs, which uses other view models for user input handling. With regard to these other view models, NewProject uses UserSelectionViewModel while NewItem uses TemplateSelectionViewModel.

In these changes, the TemplateSelectionViewModel was made to mimic the functionality of the UserSelectionViewModel, more specifically through the replacement of Groups (an ObservableCollection of TemplateGroupViewModels made to handle just one template input) with userSelectionGroups (an ObservableCollection of UserSelectionGroups made to handle multiple template inputs).

Additionally, the prototyped edit project menu includes all accurate UI ("+" symbols, counters for number of pages selected) except for the right pane, which includes the ability to remove selections and see them as they are added.

With this work, it is clear that a better starting point would be to add all entry points ('NewItem (Template Studio)' -> New Page, New Feature, etc.) into one, with the edit project wizard including a section for each. This would be very similar to the new project wizard and can thus be achieved by building on top of it instead of trying to forcibly add this functionality to the edit project wizard.

Issue: #4554

Applies to the following platforms:

• WinUI
• WPF
• UWP