Implement Compact Overlay (PiP) for Issue #180

Initial shot at implementing Compact Overlay based partially on Tim's earlier work. Adds a setting for using native Windows 10 pip instead of existing pip implementation. It should only appear on version of Windows 10 supporting compact overlay, and will be set to "on" by default on supported platforms.

Testing thus far has been performed on W10 1709 and Xbox One (to confirm the setting isn't visible).