The native packages are not required anymore, because the needed
python scripts during compile time are also provided by the
cross-compiled packages and the python scripts are platform
independent. Only the catkin package is provided as native package.

The nodelet-core recipes are updated to 1.8.1 to be in line with
https://github.com/ros/rosdistro/blob/4551e7c32d1b34984410b79bc0ec36afe3d3d245/hydro/release.yaml.

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

The nodelet_topic_tools package is required by the pcl_ros package.
Common parts of nodelet and nodelet_topic_tools are put into
nodelet-core.inc.