Plugin description

Similar to pluginlib, we will create a plugin description file called hello_ros.xml inside the nodelet_hello_ros package with the following contents:

<library path="libnodelet_hello_world"> 
<class name="nodelet_hello_world/Hello" type="nodelet_hello_world::Hello" base_class_type="nodelet::Nodelet"> 
      <description> 
      A node to duplicate a message 
      </description> 
</class> 
</library> 

Moreover, we will also add the export tag in package.xml, along with the build and runtime dependencies (optional):

<export> 
    <nodelet plugin="${prefix}/hello_ros.xml"/> 
</export>