Avoid overwriting ROS_ROOT.

Because of this, the rosconsole output was published in the
python interface.
Update README.md

Add a warning regarding the use of the sudo mode.
(complaints that the explainations were not idiot-proof)
Remove the use of dpkg-architecture.

This became useless with the last jrl-cmakemodules
synchronization.
Complete the list of packages to install for groovy and hydro.

Kudos to @aclodic for the ros-hydro-urdfdom-py dependency.
Compile and install robot_capsule_urdf for hydro. Close #19

kudos to aclodic for the hint.