Save all IPN payments as donations

Hi Rasmus,

I think the first "feature" is working: if we stop checking for the session_id, donations from "old" donors will also be stored in the Seamless Donations database. We are still checking that donations are validated from Paypal, so I think we won't have security problems.

I have also added a check so emails are not sent to old donors about the donations (just in case). Maybe we can enable this in the future.

We can discuss these changes here, or if you consider them correct, you can use the "Merge" button to move these changes to the `cs` branch.

Warm regards,
Ignacio