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

### To-do
- [ ] 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?
The window size stored in the configuration before we entered fullscreen which we will restore when we exit fullscreen. I'm not sure what to call it yet, but I intend to make some changes here so it may be replaced by something else.