Mostly UI/UX refinements.

- Fix the embarassing issue with text field becoming overlaid by the keyboard in Text annotating controller.
- Enable iTunes File Sharing support.
- Refresh content when getting back into Library.
- Ordering files in Library alphabetically.
- Add an activity indication overlay to prevent user from doing stuff during time-consuming operations.
- Update the launch images to match Library.
Close the document upon leaving Preview view controller.
Caching render results in Annotating view controller into CALayers.

Code reorganization and changes aimed on speeding up the render in Annotating view controllers. By far the best performance is gained rendering the PDF with previously added annotations into a separate CALayer and overlaying it with another full-sized layer containing the edited annotation. The technique was implemented.
New approach to renreding PDF components -- layers.

Instead of re-render pages and annotations, render manager is now able to spawn instances of CALayer (the ones for PDFPages are even cached), which interface elements can use to display the content. Appears much swifter.
Also reorganized stuff a bit in order to reduce code spaghetiness.