Support for nodelet managers

Kobuki's driver and controllers being implemented using nodelets quickly causes headaches, when starting to use namespaces. For now, we could only solve this by using absolute names for the nodelet's managers. Hence, you can't change the nodelet manager's namespace.

We need to find a way to handle this via capabilities. But how?

A first suggestion, support a ```nodelet_manager_name``` parameter in the interfaces.

Better ideas?