2021 June fix:
   visible_from output was not using the correct data, so all objectives were
   visible from waypoint0 to waypoingN. Apart from heavily impacting the
   diversity of the generated instances, this could cause some instances to be
   unsolvable (e.g. when waypoint0 and 1 are not reachable by the rover).


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Inspired by planetary rovers problems, this domain requires that a collection of rovers
navigate a planet surface, finding samples and communicating them back to a lander.

Strips: The Strips version is an interesting challenge in its own right. In addition, a
minor subtlety in the encoding is used to prevent parallel communication between rovers
and the lander: communication actions precondition on the channel to the lander being
free, and then both add and delete this fact. Because deletes occur before adds this has
the over all effect of leaving the channel free, but it makes the fact a "moving target"
which prevents a concurrent action from using the fact. Some planners find this mechanism
difficult to handle.

Useage: rovergen [-s|-t|-n|-u|-f <filename>]
                <seed> <#rovers> <#waypoints> <#objectives> <#cameras> <#n-goals>

IPC instances p01: 1 4 2 1 3
              p10: 4 7 4 6 11
              p20: 8 25 8 7 20
              p30: 10 50 8 14 25
              p40  14 100 11 15 69