Finished http request manager

Manager should apply http requests to the
main dispatch thread and return asynchronous
responses to a callback.
Added missing initiation code to req manager

Needed to initialise dictionary and requestQueue.
Also began migrating SCAPI to use req manager
Removed manual debugging,
Using Xcode breakpoint magic instead.
Renamed some methods.
reqManager.dispatchRequest:withCallback
wasn’t actually dispatching requests.
Moved and removed a ton of code in SCAPI
to use req manager instead
Removed bunch of code in AppDelegate
to use req manager to download tracks.
Made some AsyncHTTPRequest properties
read only externally.