Fixed typekit linking with rtt_roscomm libraries when building with catkin

As auto linking has been disabled in catkin builds, typekit libraries have not been linked anymore to the rtt_rostopic library. Although this usually is not a problem as the `rtt_roscomm` package is loaded before any typekit package if you use `ros.import("rtt_foo_msgs")`, this patch allows to also load typekit packages directly with plain `import("rtt_foo_msgs")` operation calls if you do not want to stream ports but only use them internally. Previously that import call failed with an error due to the unresolved symbol `ros_integration::RosPublishActivity::ros_pub_act`.

Direct (non-recursive) import of typekit packages currently also fails for typekits that contain a service proxy plugin, as the global `rosservice_registry` service is not yet loaded. But this should be easy to fix (another PR will follow)...