Consider local storage for tracking server side task state

[aarontp]

Currently the server keeps a stub for each task that gets executed so that it can check the state for these over time. If the server crashes this state gets lost so when the server restarts any Task that was outstanding that is returned will not get picked up by the server because it doesn't have a reference to it. This means that the Task will stay open indefinitely (unless "closed" manually by the user), and any clients waiting for the results from requests that generated this task will never return.

Hopefully server crashes are infrequent enough that this isn't a big issue, so we might not want/need to invest the time to save/restore this data to/from disk, but I wanted to track this issue somewhere in case this continues to come up.