Added PullableView submodule

Also, added its main class files, PullableView and StyledPullableView, to the project file.
Minor: OverlayTextLineVisRep Error message updates.
New WIP RootViewController replacement for UIPageViewController

Much like UIPageViewController, it has a current ViewController(s) that can be read and set animatingly, and has a UIPageViewControllerDelegate delegate and a UIPageViewControllerDataSource dataSource.

Unlike UIPageViewController… yeah, I'm not sure.  It's currently just a simplified UIPageViewController.

WIP because there's some commented-out code in there and other hairy stuff.

Also:
• Swapped it into AppDelegate.  It works!
Some CGAdditions we should've had ages ago.

• CGRectMakeWithOriginAndSize().  Uber-handy.
• CGRectGetMin/Mid/MaxPoint().  Also handy (especially Mid with .center).
Initial Options Drawer implementation

OptionsDrawerView PullableView-subclass created:
• Takes a contentView (the drawer's contents), settable via IBOutlet.
• Can be initialized with either a contentView or a Nib containing a View to use as the contentView.
• Sets up the PullableView's handleView, its contentView, and its own UIView state.
• Sizes and lays out all the views with some fine state logic, if I do say so myself (also, it took way too long to write, partially due to trying to do it the quick way first and failing).

Also:
• OptionsDrawer.xib IB file created; contains a basic styled view with a label and switch (for now).
• SettingsIcon.png and SettingsIcon@2x.png added, for use as the OptionsDrawerView's handle image.
• Added an instance and basic stubbed out functionality to RootViewController.

Minor:
• StyledPulableView class removed from project.  It's a single-purpose class that I think only exists for the PullableView demo.