Cleaned up @rodchile's excellent work integration OAuth 1.0 and 2.0 into RestKit. Changes
are as follows:
* Introduced new RKRequestAuthenticationType to replace the forceBasicAuthentication and other
methods for influencing how authorization works.
* Moved TDOAuth code into Vendor/
* Renamed authorization code flow classes and delegate methods for clarity.
Introduces four modes for handling background requests:
* RKRequestBackgroundPolicyNone - The default behavior replicating pre-background behavior. No special action is taken with regards to backgrounding.
* RKRequestBackgroundPolicyCancel - On transition to the background, requests with this policy set will be cancelled automatically and the delegate informed.
* RKRequestBackgroundPolicyContinue - Requests with this policy will be continued in the background after the app has been transitioned.
* RKRequestBackgroundPolicyRequeue - Requests with this policy will be cancelled and then immediately placed onto the queue for processing the next time the app is returned to the foreground.
