Add AlwaysNotifyActor option for RT::Action::Notify

Provide a way to force notifications even if they would be
prevented by the NotifyActor setting. This is useful for automated
notification jobs that might not send email as intended due to
NotifyActor settings.
Add docs for BeforeDue condition
Add new docs for reminders including rt-crontool example

The reminder docs include an example of how to schedule automatic
email for reminders using the included template and new
AlwaysNotifyActor option.
Merge branch '4.2/rt-crontool-reminders'