Refactor|Stereo 3D: Removed all public member variables of VRConfig

Now the VR configuration cvars are kept in the client, while VRConfig
stores the parameters in use.s
Documentation: Removed obsolete copyright notice

Yagisan's commit c69c83c56d77870668ccb2bdac3a90570dea384f from 2008 is
no longer relevant as the file has been completely rewritten since;
SDL is no longer used for window management.
Refactor|libhexen: Prefer the term 'hub' wrt map progression in MAPINFO

The term 'cluster' is less descriptive and map authors generally use
'hub' in any case.
Refactor|libcommon: Extracted high level savegame management into new C++ class 'SaveSlots'

At present the associated SaveInfos will continue to be owned by this
class. In the future these should be referenced from an index provided
by libdeng2's file system, which has none of the restrictions implicit
in the original games' slot-based mechanism.

Ultimately, SaveSlots will amount to little more than a mapping from
file paths into a finite set of 'slots'.

Todo: Cleanup
libcommon|SaveSlots: Added a C wrapper API for SaveSlots and made use of it
libcommon: Cleanup
libcommon|SaveSlots: Cleanup
libcommon|SaveSlots: Ensure all SaveInfos are free'd when SaveSlots is
libcommon: Catch and log errors thrown during savegame loading
libcommon|SaveInfo: Cleanup
libcommon|SaveSlots: Throw an error if an invalid savegame slot is specified
libcommon|SaveSlots: Cleanup
Merge branch 'master' into oculus-refactor
Documentation|libappfw: Added API documentation for VRConfig
Refactor|libappfw|Client|Stereo 3D: Relocated window transforms

WindowTransform and VRWindowTransform were moved to libappfw. They now
work together with BaseWindow, a new abstract base class for application
windows.

The client's VRConfig instance was relocated to BaseGuiApp, where it can
be accessed by VRWindowTransform instances.

ClientWindow implements BaseWindow.
UI|Ring Zero: Tweaks to game selection menu

The height of the game session buttons is now determined more correctly
based on the height of four lines plus the margins of the widget.

Games are now sorted by identity key rather than title (customizable
sorting is upcoming).
libappfw: Added convenience header for BaseWindow
Refactor|libdeng1|libdeng2: Relocated Garbage to libdeng2

Garbage remains a C API although it has been moved to libdeng2.
From here it is accessible everywhere. Notably, libappfw no longer
needs to link against libdeng1.

The implementation was changed to use Lockable when recycling.
Merge remote-tracking branch 'origin/master' into oculus-refactor
libgui: Added swap control for X11, debugging Canvas recreation

GLShader, GLProgram, and GLFramebuffer now support recompilation/
has any effect on the OpenGL errors occurring after switching the Canvas
(it didn't).

GuiApp has an audience that gets notified when the Canvas is recreated.

Added swap control for X11 using the GLX function for this purpose so
that Canvas recreation is not necessary when changing vsync on X11
(which was causing OpenGL errors).