Add package name to the orocos libdir also for rosbuild packages

This patch adds the project name to the orocos library directory for rosbuild packages.

As loading ROS packages has been removed from `RTT::ComponentLoader` and moved to the `rtt_ros` service (see [rtt_ros](https://github.com/jhu-lcsr-forks/rtt_ros_integration/tree/hydro-devel/rtt_ros)), the same `import(...)` method has to be used for catkin, autoproj and rosbuild packages. If the same path suffixes are used for all kind of packages, only the search path passed to `RTT::ComponentLoader::import(package, path_list)` has to be adopted accordingly (see jhu-lcsr-forks/rtt_ros_integration#13).

Independently from the library path the path where the pkg-config file is generated has been updated to `${PROJECT_SOURCE_DIR}/lib/pkgconfig`. This is the path where `orocos_find_package()` searches for these files. If the pre-Hydro behavior of writing these files directly to the package's source path is preferred, we would need to update `UseOROCOS-RTT-helpers.cmake` accordingly.