add flexible emailing+issues
Cases we want to handle with a unified email system:
- (current) customizable main messages and account info email "inclusions" for:
- creating account
- inviting user
- accepting request
- handling forgotten passwords)
- (current) change notifications
- (current) account request notification
- forms that send email to explicit email address
- forms that send email to list of addresses referred to by search or pointer
- ability to email any card