tests: explicitly declare dependencies of roslaunch tests. Fix #70.

This introduces a hard dependency on roslaunch >= v1.9.55, but that
has been released into Groovy, Hydro & Indigo. Package manifests have
been updated to build_depend on that version or newer.

The industrial_robot_client package doesn't prefix its targets, so
any package declaring a 'joint_trajectory_action' target will
satisfy the roslaunch dependency (but also shouldn't build, as it
will clash with industrial_robot_client).