Wrap initialize code in dispatch_once

This is only done for code where running it twice would actually cause a problem.

Dispatch_once is favored over a static boolean only because it seems to carry slightly more semantic information.
Refactor file chooser source selection
Recreate SCM info when re-opening file chooser

This is required for showing SCM status for “Open Files”. Previously, closing the file chooser with “Open Files” selected and re-opening it, would not have SCM info for the open files.
Enable “Uncommitted Documents” in file chooser
Add exception handler for NSManagedObjectContext’s save: method

If an exception is thrown, a dialog is shown. This isn’t very user friendly, but the goal is to call attention to the problem, as I wouldn’t expect any exceptions to be thrown by this method, but I have seen multiple “optimistic locking failure” exceptions despite single-app / single-thread access to the persistent store.
Don’t store pasteboard entries in an ordered collection

Instead we date stamp each entry and do a sorted fetch (with a limit of one) to find next/previous entry (when required).

The reason for moving away from an ordered collection is twofold, the main reason is that NSArrayController does not support ordered collections, so we lose one of the advantages of switching to CoreData. The secondary reason is that using an ordered collection requires that we use an index for “current item” (or maybe liberal use of indexOfObject:) and it’s problematic to ensure that the index is kept 100% in sync with the entries in the collection (especially with bindings and delayed actions).
Avoid property access in fetch predicate
Use @property with @dynamic for ‘primitiveOptions’ property
OakPasteboard: Setting currentEntry now updates system clipboard
Ask user to skip session restore if abnormal exit is detected