Window walker has a consistent commanding Experience

[betsegaw]

Rework internals of the app to provide consistent commanding architecture.

• Remove references in the view model to any other class other than the hotkey handler and the WindowSearchController.
• Define interface(s) for the search window in a generic and shareable way and switch the code to use them.
• Move ":quit" to be a plugin in this architecture.

[betsegaw]

Currently, the high-level architecture looks as the bellow diagram. As a first step, we need to take out the references in the view model to any class other than window search controller.