Use radians instead of degrees for joint angles

[johnwason]

Currently functions are expecting and returning degrees for joint angles, but this is causing inconsistencies because Robot Raconteur using radians and meters. Robots with prismatic joints currently will not be handled correctly.

Switch to always using radians and meters, and add utility functions to convert when required.

@maxwelllls will this change break anything with your project?

[maxwelllls]

Currently, we are still in a very early stage, and it’s easy to make modifications without any significant impact. Using the same units as the ROS system is a good idea.