add initial_space_subscriptions setting to example.ini
(re #2) summary email work
* Crontab job should call a shared function to see if user should get email
* Queue consumer should call a shared function to see if user should get email (in the case of a double queue)
* Crontab job should log how long it took to scan the account list to send emails
* Check that the email will have any content, don't send it if there isn't
* Add preference to stop emails, add footer in email body to "unsubscribe"