Show dialog when user tries to download existing dat

[dkastl]

We run into a tricky issue when the user tries to download the same DAT more than once: Should we add the new download to the list? Should we download it a second time to the folder?

The easiest solution for this would be to simply show an alert dialog:

alert('This DAT is already added to the list.')

and:

alert('This DAT has already been download. Using the downloaded version')

... in case that DAT exists on the Hard-disc but not in the DAT list.

[martinheidegger]

The dialog has been added and tested - quite a bit.

Sorry, closed prematurely: Mistook this with another issue.