[ROS-O] add missing pluginlib dependency

[v4hn]

This is required to compile with debian's pluginlib-dev package which isolates the headers.
The include is required here and here.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 19.89%. Comparing base (8703caf) to head (3fc4537).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #252   +/-   ##
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  Coverage   19.89%   19.89%           
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  Files           5        5           
  Lines        1739     1739           
=======================================
  Hits          346      346           
  Misses       1393     1393           

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[v4hn]

ping @henningkayser .

[rhaschke]

Ping @henningkayser

[nbbrooks]

Shouldn't pluginlib also be added to CATKIN_DEPENDS?

[rhaschke]

CATKIN_DEPENDS lists dependencies forwarded to downstream packages. pluginlib is used for plugins, which usually don't have downstream dependencies.

[nbbrooks]

The uses of the pluginlib header are in cpp files and not the headers so I do not think it should be added for that reason.

[rhaschke]

@nbbrooks Can you also merge, please?