Outdated instructions for launching moveit_rviz.launch

[ljden]

The readme still says to run the moveit_rviz.launch with config:=true, however the interface has changed with the recent updates:

universal_robot/ur5e_moveit_config/launch/moveit_rviz.launch

Lines 7 to 9 in 09a637d

	<arg name="rviz_config" default="" />
	<arg if="$(eval rviz_config=='')" name="command_args" value="" />
	<arg unless="$(eval rviz_config=='')" name="command_args" value="-d $(arg rviz_config)" />

From UniversalRobots/Universal_Robots_ROS_Driver#403 (comment) it seems like config:=true should be config:=$(rospack find ur5_moveit_config)/launch/moveit.rviz

I will open a separate issue regarding moveit.rviz defaulting to the endeffector group rather than manipulator

[fmauch]

The main README file has indeed not been touched, yet and should get some overhaul.

[fmauch]

This is covered upstream and should be covered by ros-industrial#538