Add Follow planner, a dumb global planner to follow stuff

Right now it doesn't do much.

It takes a `geometry_msg/PoseStamped` as an input, and outputs a straight path to go from the robot's current location to the goal.

It publishes the path for visualization purposes under `/move_base/FollowPlanner/plan`

Also, a commit to remove `pal_emergency_stop` from this repo has slipped in. It is completely harmless and should be done anyway.

@efernandez @awesomebytes @RainCT