D3D: Add exclusive fullscreen support.

This PR adds support for exclusive fullscreen when "Render to Main Window" is disabled. Please test it out and provide me with some feedback so I can polish things were necessary.

Build available at: https://dl.dolphin-emu.org/prs/pr-506-dolphin-latest-x64.7z

### Changes
- Makes exclusive fullscreen support the default fullscreen mode for D3D.
- Exits fullscreen when the stop confirmation is shown and exclusive mode is active.
- Removes CPanel so the separate RenderFrame is now  a top-level window with no childs.
- Adds a borderless fullscreen option in the advanced video configuration to switch back to the old fullscreen behaviour.
- Removes a redundant hack for 3D Vision.
- Fixes the D3D renderer choosing the wrong refresh rate upon initialization. It now chooses the appropriate refresh rate for the current desktop resolution.

### To-do
- [x] Restore original window size when switching back from fullscreen.
- [x] Set fullscreen upon initialization of the backend if it is enabled.
- [x] Restore exclusive fullscreen when focus is returned after Alt+Tab.
- [x] Fix deadlock when stopping emulation in fullscreen. (PR #515)

### Considerations
Will exclusive fullscreen be an option or always on? Would such an option will be the default or optional?

At this moment I consider support for OpenGL or "Render to Main Window" outside of the scope of this PR, unless such support is considered essential before adding this feature.

### Fixed issues

Issue [6713](https://code.google.com/p/dolphin-emu/issues/detail?id=6713) and [7334](https://code.google.com/p/dolphin-emu/issues/detail?id=7334) should be fixed by this change.

3D vision support is restored in DX11 with a much cleaner implementation which fixes issues [3979](https://code.google.com/p/dolphin-emu/issues/detail?id=3979), [4726](https://code.google.com/p/dolphin-emu/issues/detail?id=4726), [4732](https://code.google.com/p/dolphin-emu/issues/detail?id=4732) and [5990](https://code.google.com/p/dolphin-emu/issues/detail?id=5990).

It may also help Nvidia Optimus detect Dolphin as an application that requires high performance, can anyone test that?
I'll change the behaviour of the Borderless Fullscreen option to ensure it is enabled when the backend does not support exclusive mode. I'll add `bFullscreen` to this function and then use it in the renderer to check if exclusive fullscreen is enabled.