I fixed an issue regarding multithreading and the push navigation between the ticket list and the detail view.

Originally I had the API request thread launch the segue, but that led to issues where the navigation controllers would get all wonky sometimes (race condition). Now the item list thread will launch the detail view immediately, and the API COMM will update it when the information is ready.
Now able to pull individual items out of the persistent store.

When the internet is not connected, items which have been previously viewed are now pulled out of the persistent store. If they have not been viewed, a message is displayed to the user telling them that we do not have the complete ticket information. The edit button is also disabled when the detail view is opened during a period of no connection. Currently no handling for the case where the user loses internet while the detail view is open.

More descriptive update messages are now shown when the user pulls down to refresh, telling the user when the list was last updated (now stored in coredata) so that they know how stale the information is.