Successfully rebased onto 0.2.2
Download results stored in static variables.

ProviderAPI has now 3 different static variables, each one for the 3 files that have to be downloaded to set up a provider.
Save my work until now
Retry button on failed downloads.

Next step: remove the provider from the list (big security hole, since all providers present on the list are assumed to be secure).
Not added item is removed after canceling dialog.
Cleaner error message.
JavaDoc for pickErrorMessage
Retry button prompts new provider dialog.

The user can change the new provider's data entered before failing.
New provider dialog remembers previous data.

It also (supposedly, I didn't test because Bitmask is working ok from our client point of view) distinguishes between cancelling a new custom provider and cancelling a preseeded provider.
Rebased onto current develop.
Rebased onto 0.2.2