Refs #126. Background moc -> private
Refs #126. Protect lazy moc initialization with dispatch_once
Ref #126 Fixed threading errors.
Refs #126 Removed double sync dispatch to main queue, to remove deadlock.
Refs #126 dispatch_async for all delegate calls instead of dispatch_sync
Refs #126 Remove network calls from the sub-retrievers (EMSSlotRetriever, EMSSpeakerRetriever and the likes) and put it in EMSRetriever instead.
Split conferences to root and conferences.
#Refs 126 Deleted extra call to  [[EMSAppDelegate sharedAppDelegate] stopNetwork];
Refs #126 Use NSURLSession instance variable.
Refactor retriever to parser
Split retrievers delegate into speakers retrievers delegate and parser delegate.
Split parser delegate
Refs #126 Updated logic for session, slot, room saving dependency. Download and parsing of these can now happen in parallel, but saving of sessions still waits until slots and rooms are saved.
Add error to root parser
Fix compile
Error for parser delegates
Add finshedConferencesWithError
More error handling
Refs #126 Use separate url sessions and parsing queues for conference, sessions and speaker sync. Cancel pending operations on error.
Refs #126 Start refresh of conferences and rely on the mechanism to auto-select latest conference if user tries to refresh sessions when no conference has been selected.

This fixes a lot of issues we previously had. For instance; Trying to refresh sessions if no conferences was loaded would previously not work. Users would have to understand that he had to go to settings and load conferences first. This situation was easy to get into if app was initially loaded with no internet connection.