Fixes issue #587. Apparently, self.interfaceOrientation is unreliable.
Fix: freeze on "restore purchases" error
Refactored notification observer setup
Sorted files for XCode

This is to put Constants.h and UIConstants.h in a more prominent position.
* Fixes issue #578
* -fadeOut was called by -willRotateToInterfaceOrientation, but -fadeIn was never called as it's part of didRotateFromInterfaceOrientation
Refactored references to PurchasesManager
Partial fix for #574

1. Open shelf
2. Read downloaded book
3. Select "Back to Baker Shelf"
4. Read the same book again
5. Select "Back to Baker Shelf"
6. Crash
Merge pull request #676 from waywalker/issue-578-no-index-view-after-modal

Fixes #578
Use shelf cover as a Newsstand icon
Better error management when retrieving shelf JSON
Fixed compilation errors in Standalone mode
Removed double IssuesManager initialisation
Better download management for shelf JSON

Closes #663.
Create JSON status files on init

This has the fortunate side effect of removing a lot of misleading "error when loading" messages from the log.
Fix for crash when releasing modal web view

Fixes #574:
1. Open shelf.
2. Read a downloaded book.
3. Click on a link in the book that opens up the modal web viewer.
4. Click Back on the modal web viewer to close it.
5. Without doing anything else, double tap on the book page to bring up the index and navigation.
6. Select "Back to Baker Shelf"
7. Crash
Merge pull request #673 from waywalker/issue-587-index-view-orientation

Fixes issue #587. Apparently, self.interfaceOrientation is unreliable.
Added method to return latest issue
Refactored ShelfViewController init methods

The `init` method was never called and `initWithoutBooks` was pretty much doing what an `init` is supposed to do.
Consolidated ShelfManager methods in IssuesManager
Refactored IssuesManager into a singleton