Add "rate" check on PID to make sure consecutive servo commands are reasonable

[adeguet1]

The goal is to make sure the trajectories requested by the user are somewhat continuous. We might even be able to use the max velocity used for joint trajectory generation (maybe with extra 20% to avoid false negative). For now, I would replicate implementation for PID tracking error, i.e.:

• Limits hard coded in arm derived classes
• Send rate limits to PID using provided interface
• Command to enable/disable rate limits, including check mark in PID Qt widget