Fix CMP0007 policy problem + .catkin removal in case of catkin package.

This commit fix a problem when a package is both a jrl-cmakemodules package and a catkin
package (see dynamic_graph_bridge_msgs).
This fix a CMP0007 policy problem, and remove the .catkin file put in the _inst directory during distcheck.
The file is not in the list of installed_files and is not removed, making the test for proper uninstall failed.