Add a node that calls an external planner

[dgerod]

Create a node that implement planner interface of ROSPlan, that's calls an external planner (e.g. FF). It should be able to select from a set of ready planner without modifying the code. Following automatic load of actions in action_interface.

This code should be added to src/ros/interfaces/planner_interface and a node that use it will be created inside non existing directory node