Add monthly donations processing script.

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Mail template for monthly mails
Print better error messages plus some other cleanups.

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Create a new recurring Order after payment has been started.

This commit also includes some small cleanups and bug fixes.

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Integrate mailing into monthly donation script.

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Display summary of errors at the end of the script.

Also add option to disable emails (for testing).

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Create correct payment object for status report.

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Only display error report when there are errors.

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Disable OpenIBAN conversions by default.

The test service has incorrect and incomplete data.

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Fix test failures caused by previous changes.

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Admin improvements for RecurringDirectDebitPayment.

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Don't filter out donations less than €1.13 in csv generation.

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Order the projects by popularity correctly.

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Skip monthly donations that may have been already processed.

This commit also includes a few cleanup from @gannetson's review.

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Merge pull request #726 from benkonrath/monthly-donations-process

Monthly donations process