Added controllers stopper

This node takes care about taking down and restarting controllers based on
the robot's state.

Closes #48

controller_stopper/README.md

@@ -0,0 +1,32 @@
+# controller_stopper
+
+A small helper node that stops and restarts ROS controllers based on a boolean status topic.
+
+When the status goes to `false`, all running controllers except a set of predefined
+*consistent_controllers* get stopped. If status returns to `true` the stopped controllers are
+restarted.
+
+## Nodes
+### controller_stopper_node
+
+
+
+#### Parameters
+ * **"consistent_controllers (list of strings)"**
+
+    Consistent controllers will not be stopped when the robot stops. Defaults to  ["joint_state_controller"]
+
+#### Service Clients
+ * **"controller_manager/list_controllers"** ([controller_manager_msgs::ListControllers](http://docs.ros.org/api/controller_manager_msgs/html/srv/ListControllers.html))
+
+    Controller manager service to list controllers
+
+ * **"controller_manager/switch_controller"** ([controller_manager_msgs::SwitchController](http://docs.ros.org/api/controller_manager_msgs/html/srv/SwitchController.html))
+
+    Controller manager service to switch controllers
+
+#### Subscribed topics
+ * **"robot_running"** ([std_msgs::Bool](http://docs.ros.org/api/std_msgs/html/msg/Bool.html))
+
+    Subscribes to a robot's running state topic. Ideally this topic is latched and only publishes  on changes. However, this node only reacts on state changes, so a state published each cycle  would also be fine.
+