Add a relation for notified users in jobs
GET and POST for notified users in jobs
Add some tests for notified users in jobs
DELETE for notified user in job
Unpack notified_users relationship in jobs
Allow including notified users in new job
Notify interested users on job completion
Return output directly, without intermediate var
User filter_by() where possible.
Rework logging for completion mails
Get header From address from configuration
Simplify getting list of email recipients
Use set for assigned agents

Using a set instead of a list for keeping track of which agents have had
tasks assigned to them during the current scheduler run is the more
logical choice and makes it impossible to accidentally have an agent in
there twice for whatever reason.
Merge pull request #161 from guidow/set_for_assigned_agents

Use set for assigned agents
Merge pull request #158 from guidow/email_notification

Email notification