Diff drive open loop odom

This PR is an update from the hydro-devel branch of ros_controllers from PAL Robotics.

> The purpose of this PR is to support open loop odometry when there are no encoders.
> It basically adds:

> * open_loop param
> * extends Odometry class to update using the last linear and angular velocities received by the controller, i.e. set the odometry twist directly with then and integrate the position (x, y)


Related PR:
https://github.com/pal-robotics/ros_controllers/pull/39