Allow backends to specify the views they want to use

Different backeds may want to overide the default view provided by the vcs api. We need a simple registry that provides default views out of the box and then backend modules can override these if they want to.

Also, we can always add an interface for selecting a different view to either vcs api or the backends if we want that later. For now they will just be views that can be modified through the UI by users later if necessary.

Do we want to provide any kind of hook that can be used to modify that?