On-the-fly point streaming and Cartesian jog

I have implemented on-the-fly point streaming to the controller via the joint_command topic. The approach very closely emulates the way that trajectories are currently sent to the controller. I have also included a Cartesian jogging package that uses this new functionality. There is a rogue source file called keyboard_teleop_node.cpp that is not part of any package. It is example code that does Cartesian jogging from the keyboard.

Some code might be rough around the edges with extraneous comments and the like, but I thought I'd offer it up to anyone who might be able to use it.