Measure Tool "Enhancements"

[Jmeyer1292]

I would like to change the default measure tool to display the X, Y, and Z components of the selected ray. I draw this inspiration from SolidWorks, a professional solid modeling package.

Please see a plugin I wrote: rviz_distance_tool. There's a GIF on the front page that illustrates the idea.

If it's of interest, I'll submit my code as a PR.

[rhaschke]

Looks great. Yes, please file a PR.