Changed SceneViewControllerForGLK to a UIViewController and patched in a GLKViewController sub-controller

SceneViewControllerForGLK now inherits from UIViewController, and owns a SceneGLKViewController instance (new GLKViewController sub-class) which it inserts as a sub-viewcontroller, and uses for delegation for SceneViewControllerProtocol responsibilities.  SceneGLKViewController handles more of the GL-specific stuff now, and owns the context and baseEffect.  SceneViewControllerForGLK now uses just a plain-old UIView as its container for the GLKViewController's GLKView.

Related changes:
• SceneViewControllerForCG header cleaned up by moving a bunch of this stuff to SceneViewControllerProtocol; this is stuff that all SceneViewControllerFor…s should implement.
• SceneViewControllerForGLK now acts as a delegate for both the GLKViewController and the GLKView, and adheres to both protocols.
• SceneViewControllerForGLK also now counts as a container view container, and uses the blessed methods for container use only.
• Added a little more possible-error-reporting to SceneGLKViewController's GL setup.  The GLK sample I copied this from is just a little too loose in its object management for me, but I'm not into rethinking the whole thing this very minute.
• The `self.scene = aScene` initializer argument assignment moved before the initCommon call.  This seems to make more sense as a whole, and helped some too-late side-effects.

Clean-up:
• Removed _vertexArray/Buffer_glObjectName ivars.  They weren't being used and haven't been for quite a while.
• Removed isContextThe

Known issues:
• SceneForGLK's baseEffect is set (by SceneViewControllerForGLK) from SceneGLKViewController's hidden baseEffect property, which works but emits a compiler warning.
	» I'm still not sure if BaseEffects are supposed to be shared or created roughly one per vertex array.
• What looks to be a single draw is missed when switching from CoreGraphics to OpenGL.  This could be an issue with RootViewController not being as solid as UIPageViewController was, or with the handling of contexts and GL stuff.  Or otherwise.
Merge branch 'master' into refactor/sub-GLKViewController

Resolved minor conflicts in:
	App/Controllers/SceneViewControllerForGLK.m
Fixed GLK draw preempting

Two issues were happening here.

First, SceneViewControllerForGLK's view was a plain-ol UIView, which doesn't understand what to do when told to “display”.  It's now an instance of our SceneView class.

As a side-effect, SceneView can now take a drawingView which it'll delegate draws to, one way or another.  In this case, we're setting the drawingView to the GLKView subview so it delegates the display call to the GLKView's layer, and onto the proper drawing procedures.

Second, the pre-empted drawing was too early (prior to the Scene's baseEffect), causing GL errors.  While avoiding this is best, it also shouldn't be breaking.  SceneForGLK's drawForView: now has a guard that'll spit a warning and bail if baseEffect isn't present (yet).

Also:
• SceneView's properties have been changed from assign to unsafe_unretained ownership to signify that we need to be careful with these.  Also, usages of these properties now have balanced sets and unsets.
• For organization, AppDelegate's draw pre-empting broken out into a pair of internal sub-methods.

Note: With this new SceneView usage, the SceneViewControllers have grown even more similar.  Merging most of this into a parent class should be child's cake.
Merge update 'refactor/sub-GLKViewController' to branch 'master'
Minor: Made SceneViewControllerForGLK a presentation context

…since it's a container.  And that's what the iOS docs recommend.
Merge branch 'refactor/sub-GLKViewController'