OcTree bounding box pruning

[TheBrewCrew]

This adds an optional pruning size and height to the Octomap in MoveIt perception. This pull request depends on pull request #593. This feature is enabled if the octomap_size_limit param is set. octomap_height_limit can be set to specify a height limit on the Octomap. As the robot moves, the bounding box center will be set to the root link transform and then the Octomap will be pruned to fit inside the bounding box, marking data outside the bounding box unknown and freeing up memory. This will keep the Octomap to a reasonable size as the robot moves so that the Octomap can be passed across the network faster.

[davetcoleman]

I wish I knew more about this part of MoveIt! to review