ros-workspace installs its setup scripts under <prefix>, which is an
unnatural location when <prefix> is /usr. Move them to be under
<sysconfdir>/profile.d/ros and create "ros_" prefixed symlinks to them
under <bindir>. If "ros-workspace-implicit" appears in DISTRO_FEATURES,
create a ros.sh that sources ros/setup.sh, thereby setting up the ROS
workspace for every login shell.