Feature/reconnect delegates for background

Too my knowledge AFNetworking does not have a way to hook back up progress delegates for uploads when an app relaunches and has tasks processing in the background. This is my attempt at adding that functionality.

The idea behind my approach was to add a mechanism to start the NSOperationQueue for processing delegate messages in a suspended state when the AFURLSessionManager gets unarchived from initWithCoder. This would allow me reconnect handlers at my leisure. I also had to add something to allow me to re-associate a NSProgress object and a completion handler with an upload task since that was all done in creating an upload task.

I would love to hear your feedback!