Show a list of affected children in the host/service detail if it has a problem and is part of a dependency

[nilmerg]

As a complement to #1050, we want to list the most severe children that are affected by a parent in its detail area.

It should look like this:

Notes

• The list may contain objects of type host, service and redundancy group
• It is shown if any of the dependencies, the object is the parent of, have failed
• Only direct children and only those whose dependency has failed are listed
  • Results are ordered by severity, if applicable
  • Restrictions apply as usual
• Each item links to its detail area
  • Redundancy groups have none yet (See Add a detail view for redundancy groups #1056)
• Results are limited to 5 in total
  • A link to all results if there are more is shown (See List views for parents and children #1063)
• The list is entirely replaceable by hooks of type ObjectDetailExtensionHook
  • It is located in the RELATED section and uses the position 510