Notifications Source: Honor Host and Service enable_notifications

[oxzi]

In Icinga 2, both the Host and Service object have an enable_notifications attribute. This can be altered during runtime, even via Icinga DB Web, as recently reported in the community forum.

Objects with disabled Icinga 2 notifications should not result in a notification being created from Icinga Notifications.

[nilmerg]

Icinga DB is responsible for this now. Moving.