Added missing orocos_generate_package() calls

For the RTT message packages in rtt_ros_comm the .pc-files have been missing so far.
Or would it better to use the `rtt_roscomm_generate_package()` cmake function instead of `ros_generate_rtt_typekit()`? But this would produce warnings on missing .srv files.

The current version of rtt_common_msgs does this, too:
```
SEND_WARNINGros_generate_rtt_service_proxies: Could not find any .srv files in the trajectory_msgs package.
```

I personally would prefer to remove the  `rtt_roscomm_generate_package()` function in rtt_roscomm and do the `orocos_generate_package()` call to the package template. The user could uncomment the `ros_generate_rtt_service_proxies()` line only if required.