catkin.class: adding package.xml to the shipped packages for rosversion

The rosversion command requires that the package.xml are available at
run time. The rosversion command is used when starting roscore.
roslaunch: improving runtime dependency
core-image-ros-groovy-running-roscore: augmenting hosts
roslaunch: adding coreutils as roslaunch needs its du command (resolves #60)
signaling that the running-roscore image is for testing with qemu and x86 setup
Merge pull request #63 from bulwahn/master

some minor improvements towards running roscore