SelectedClusterPublisher: a nodelet to publith the points inside of the selected box

add new nodelet `jsk_pcl/SelectedClusterPublisher` to publish the points of the cluster specified by `jsk_pcl_ros/Int32Stamped`.

this nodelet is supposed to be used with `jsk_interactive_marker/bounding_box_marker`.

Red points are the pointclouds selected via `jsk_interactive_marker/bounding_box_marker
![screenshot_from_2014-05-27 19 39 29](https://cloud.githubusercontent.com/assets/40454/3090356/4301b974-e58b-11e3-89b1-1349b5df6d88.png)
![screenshot_from_2014-05-27 19 39 33](https://cloud.githubusercontent.com/assets/40454/3090357/4301c48c-e58b-11e3-9450-6d8c049d0aa9.png)

`.