(FR #986) mailing job to apologize for May 2013 PayPal recurring fail.

Incidentally created a "oneoffs" module to house this sorta stuff.

TODO: need the letter subject and body

Change-Id: Ic9ce7d36eeee0f9bbcbbdab65a578dd9f10d6b2c
Merge "(FR #986) mailing job to apologize for May 2013 PayPal recurring fail."