wxUiTesting: Expand client area to support logging window, notebook

Description:

Our testing app doesn't currently do anything with it's client area. One thing that might be useful would be to add the same kind of logging that we do with MsgFrame in wxUiEditor, only using the client area for the output instead of a child window.

Taking this one step further would be to create a splitter window as the client with the logging window on the left, and a wxPanel on the right. The panel could contain a notebook, with tabs covering specific dialogs, or just the actual test controls in some cases. The logging window on the left could actually be a panel as well so that we could have a toolbar with toggle buttons for the logging types, along with clear and save buttons.