Arbiter does not continue caching an AOI if the previous AOI did not finish.

[garnertb]

If a user exits Arbiter while the app is caching tiles the application will not resume downloading tiles when the user opens the application again. Arbiter should allow you to cache remaining tiles that weren’t picked up on the first time. Also, if expanding the AOI, would be good to only grab the delta tiles (if the AOI is expanded from the first cache). Users should have option to recache the entire thing in case they want to grab a fresh set of tiles.

To reproduce:

1. Open Arbiter and click the red box to create a new AOI.
2. While the tiles are downloading close Arbiter.
3. Open Arbiter, tiles that have already downloaded are shown but Arbiter will not prompt you to finish caching.

[smesdaghi]

At the very least, user can be warned that caching tiles had not completed successfully and give the user option to cache again.

[danpalumbo]

Tried to reproduce. Arbiter returned to the cache exercise when I re-opened Arbiter, but part the AOI was not cached. It was blank on the screen. This should remain open. (DP)