A skip program line or continue option

[RyanPaulMcKenna]

Feature summary

Add continue and skip options to /ur_hardware_interface/dashboard/. Currently we can start and stop programs like so; rosservice call /ur_hardware_interface/dashboard/play rosservice call /ur_hardware_interface/dashboard//stop

It would be good to be able to skip a single line of a program or have play from line or jump to the next line.

The reason I think this would be useful is it would allow us to use the external control urcap program and then when we want to do other things that external control can't support we can skip past or continue past that line.