Removed env-hook from orocos_toolchain and added package-specific env-ho...

This is a follow-up of #4. I completely removed the env-hook from the orocos_toolchain meta package and added them in the following packages instead:

* For [rtt](https://github.com/orocos-toolchain/rtt/commit/d821d7d3ca6318114943c90b7f95ad6b29c54fa6) (copied @jbohren's env-hook from the [rtt_ros](https://github.com/orocos-toolchain/rtt_ros_integration/tree/hydro-devel/rtt_ros) package)
  * sets the `OROCOS_TARGET` variable
  * sets the `RTT_COMPONENT_PATH` by appending `/orocos/$OROCOS_TARGET` to each entry in `LD_LIBRARY_PATH`
* For [ocl](https://github.com/orocos-toolchain/ocl/commit/cd8b5b33c26311aac5a667372788e07b7ffeafc6):
  * set the `LUA_PATH`
* For [utilrb](https://github.com/orocos-toolchain/utilrb/commit/3d1aefd4224ff17f997b50665bab685184f8c285):
  * set the `RUBYLIB` variable
  * This package is a dependency of orogen and typelib, so the env-hook would be effective for both.
* For [typelib](https://github.com/orocos-toolchain/typelib/commit/70c2dc3bb48052903e4f4af82148e3e7a2bac722):
  * Currently only sets the `TYPELIB_USE_GCCXML` variable.
  * I am not sure if the `install/lib/typelib` directory still has to be added to the `LD_LIBRARY_PATH`, as typelib seems to use proper RPATH settings and there is nothing like this in [orocos_toolchain/env.sh](https://github.com/orocos-toolchain/orocos_toolchain/blob/master/env.sh). It's currently commented in [00.typelib.sh.in](https://github.com/orocos-toolchain/typelib/blob/70c2dc3bb48052903e4f4af82148e3e7a2bac722/env-hooks/00.typelib.sh.in).

Note that these new env-hooks are only effective if the packages are installed to a catkin install-space, e.g. together with the orocos_toolchain metapackage or if ROS binaries are generated on the ROS buildfarm. `catkin_make_isolated` without `--install` will not work as each package has it's own installation directory and the generated setup files for pure cmake packages do not look for catkin env-hooks in `etc/catkin/profile.d`. For non-catkin setups, you still have to source the env.sh script.

This env-hook splitting is required as installation of a package that requires rtt will only install `ros-hydro-rtt` and its dependencies, but not `ros-hydro-orocos-toolchain` in ROS hydro and upwards and the env-hook in the orocos_toolchain metapackage would not be available.