Improve base_controller

[jubeira]

A general review of the code should be performed. The module has some details that can be improved without an excessive effort.

• The basic code publishes the odometry at 10 Hz using standard thread functions. This can be improved using higher rates and ROS Rate functions. The rate could be configurable too.
• Some of the transformations being published are not necessary (e.g. laser_link).
• The basic code publishes odometry using base_link as its target frame. The name could be configurable somehow (for example, publishing base_footprint proved to be useful in tests).
• General cleanup of "To Do"s.