Inconsistent behavior without multi-window feature

[ids1024]

If the multi-window feature isn't used, it is still possible to create windows, but all of them use view instead of view_window. And the no_main_window setting is ignored.

If we want to allow use without this feature, we probably want view_window, no_main_window, and commands that create windows to depend on the multi-window feature. But it may be best to just only support that mode.