missing pluginlib xml files for each controller

[Karsten1987]

With #19 the individual controllers can't be loaded anymore as the according plugin.xml file is missing.

@jordan-palacios : How did you test to load the controllers in the controller manager? Maybe I am missing something here.

[jordan-palacios]

@jordan-palacios : How did you test to load the controllers in the controller manager? Maybe I am missing something here.

Controller loading was validated using the test_controller.

There are no tests for controller loading of each individual controller though and I missed adding the plugin.xml files in #19. I'll fix that and also add loading tests for each controller.