[NOTIFICATIONS] Send notifications to all admin users

[josegonzalez]

For notifications, we should:

• [x] Make notifications configurable in a db table of some sort
• [ ] Give a panel to turn on/off certain notifications
• [ ] Link to it on the appropriate pages

For admins we should:

• [ ] Modify any notification jobs to send to all admin users
• [ ] Add a link to notification emails to modify your notification settings