Provide list of units with lost position

[robo-w]

Extend status response with list of units, where the position was lost. Provide the list with a reduced unit view with:

• unit ID
• unit name

A unit shall be marked as "position lost", if no position update was received in the last interval of "default maximum data age". If no position update was received for longer then the retention time, the unit shall be no longer marked as "position lost".