reloading planner configurations before each solve()

[drchrislewis]

The mechanism for loading parameters from the ROS parameter server of the ompl_interface is a protected function loadPlannerConfigurations() run only on construction. Many planner parameters drastically change the performance of the planner, and it would be nice to be able to change these on the fly without having to restart the move_group node. For example, the parameter "range" indicates how far toward some random c-space point the random planner will attempt to move to create each waypoint. When this value is small, one tends to get intricate plans closely skirting objects. When it is large, the plans tend to move way out of the way.