Add prevent_look_ahead_poses_near_goal to fix oscillation

[howardcochran]

In testing, I found that setting the new parameter control_look_ahead_poses to 3 improved path following accuracy very much. However, in cases where need to arrive at a very precise goal (as by setting xy_goal_tolerance to 0.01), it could cause the robot to overshoot the goal and then oscillate back and forth over the goal indefinitely.

This new parameter fixes that by preventing control_look_ahead_poses from selecting one of the last few poses of the path.

Since this new dynamic parameter affects the behavior of an existing parameter, it makes sense to make the existing one dynamic also. For completeness, I made all remaining parameters in the trajectory group be dynamic, as there is no reason I can see not to do that.

[corot]

Hey, thanks for the PR; very valuable. I open another PR to melodic. I suppose you don't care anymore about merging this to kinetic, right?