(acceptancetest_hironx.py) Add tasks written in ROS. Add ROS client.

Some tasks that involve `Cartesian` and didn't look straightforward in ROS, are not implemented yet (task 4, 7). 

At this time `ROS_Client` class is added for the first time. This class provides simplified low-level ROS API (using `pr2_controllers_msgs.msg.JointTrajectoryAction`) for Hiro-NXO robot. Features available at this moment are still minimum, but as seen in task 6 in acceptance test py, interruption is achieved.

As mentioned above what's still missing is Cartesian control, which is possible with the same ROS interface, `JointTrajectoryAction`. [Explained in this tutorial](http://wiki.ros.org/pr2_controllers/Tutorials/Moving%20the%20arm%20through%20a%20Cartesian%20pose%20trajectory), though, it requires to create a `ROS Service` type, so `HrpsysConfigurator.setTargetRelative` seems simpler.

That said, I'm wondering whether (a) I should manage to implement task 4 and 7 in ROS or (b) leave Cartesian features to `hrpsys`. 

If we choose (b), a unified client class that provides all available features while encapsulating the detail of both hrpsys and ROS might be very useful for the users.
Also, creating a unified class doesn't mean users wouldn't be able to write directly in `hrpsys` nor `ROS`; API of those are still open to users.