Resume job processing on app restart

[markmhendrickson]

This entails modifying job processing so that all jobs that have been started but have not finished queuing up all intended item storage kue jobs will resume their processing upon app restart.

For example, if a new job with name storeAllItemsForUserStorageSourceContentType is saved but only 50 of 100 available pages from the source for the content type have been retrieved for initiation of item storage kue jobs, the 51st and subsequent pages of data should be processed upon app restart.

This change goes hand in hand with #70 to ensure that jobs store all intended items even if the app restarts in the meantime (because of a code deployment or any other reason).