Only allow manually setting focus to the rendering widget when in Single Window mode. Apply this behavior to when changing the mode while an app is running.

By default widgets are set to the focus policy Qt::NoFocus which disallows manually focusing it. Changing the policy to allow clicking the widget to set focus to it allows for keyboard input when not rendering to a popout window. This commit also sets focus to the widget when showing it.

Fixes issue #158.

The window title is none of the emulation core's business. The GUI code is free to put whatever it wants there.
Providing properly thread-safe window title getters and setters is a mess anyway.

The view is scaled to be as large as possible, without changing the aspect, within the bounds of the window.
On "retina" displays, or other displays where window units != pixels, the view should no longer draw incorrectly.

This was automated using `clang-modernize`.

This should fix context creation on OS X. Also requests a core context on all platforms in Citra-GLFW, for consistency.

Uses QSettings on citra-qt, and inih on citra-cli.

Note: There is a pre-existing issue with booting a new game in that it keeps the old EmuThread.
The GL code now supports this but the Core still doesn't.

Connect the emu_thread start/finish to a moveContext slot.

Changed QGL version to 3,2 in order to be less restrictive, yet it should still change up to 4,1 on OSX on Qt5.