Fix a comment typo
AFURLConnectionOperation: Add optional userInfo parameter to allow the caller to pass options to the initializer from AFHTTPClient methods

Sometimes operations have options which affect processing.

For example, the programmer could subclass `AFJSONRequestOperation `and override the initializer to pull a value from `userInfo` to set `JSONReadingOptions`.

In my application I use this to pass a processing queue and managed object context to the operation.
Change type of userInfo parameter to leverage existing property
Use a #define to avoid code duplication for UIImage and NSImage

Conflicts:
	AFNetworking/AFImageRequestOperation.m
AFHTTPRequestOperation subclasses: Refactor code which supports processing to an intermediate class AFHTTPRequestProcessingOperation

The goal of these changes it to make it simpler and more obvious to implement a processing subclass, to simplify the code, and avoid code duplication.

All processing is now done in `-processResponse` which is invoked from the completion block. The processing code shares a single dispatch queue, though the queue can be overridden for a given operation.

For naming clarity, the imageProcessingBlock is now called filterBlock. That block is now a property and, when set will be invoked during processing.