Add option to exclude recurring donors from donors script
I want to be able to send a custom message to people who didn't have a recurring donation, pretty much the opposite of the current -r option.
If across the same period, someone had made both a one-time and a recurring donation (in whatever order), it should be excluded from the list as well:
- If these people configured the recurring donation after the one-time donation, we're happy already.
- If these people made a one-time recurrding donation after possibly cancelling a recurring donation, we don't want to bother them again.
- If these people made a one-time donation on top of a recurring donation, we're happy as well.