Enable nodelet support

So far nodelets have been quite a headache with apps. This PR will make our lives easier by utilising the newly implemented nodelet support by the capability server.

From now on all nodelets - both app and cap nodelets - are loaded into the capability server's nodelet manager. This is done automatically by using the right parameter in the app launch file, e.g. https://github.com/yujinrobot/kobuki/blob/caps_updates/kobuki_apps/rapps/random_walker/random_walker.launch.xml#L2

This PR resolves #115 and resolves #119.

**NOTE**: This PR already contains the changes in PR #159. Please merge that one first.