Cleanup/restructure ur_bringup

[gavanderhoorn]

ur_bringup contains too many launch files, some of which are most likely no longer needed (such as the joint_limited variants).

Ideally there would be either a single launch file per robot variant, or even a single launch file that accepts a variant or model argument and loads the appropriate parameters and other launch files based on that.

Another issue to consider would be what to do with ur_bringup in general seeing as it's only actually usable with CB1 and CB2 controllers (due to the hard-dependency on ur_driver).

[gavanderhoorn]

Related discusion about robot drivers and bringup packages: ros-industrial/ros_industrial_issues#49.

[gavanderhoorn]

And related PRs (joint limits): #268 and #266.

[gavanderhoorn]

This package has actually been removed, as the drivers would now be responsible for providing these .launch files.

Closing as a wontfix.