This consolidates the UI code for NDOF input settings, making all settings accessible from the preferences.
This works around an issue where the Space Navigator's "Menu" button doesn't trigger the menu in Blender.
There's also no good reason not to make all preferences available in the preferences window.
I also took the opportunity to redo the UI layout which was quite a mess:
| Preferences | 2D View | 3D View | |
| Before | |||
| After |





