Improve agitator control/unjamming

[calebchalmers]

There are some shortfalls with the current implementation of agitator unjamming which will require some changes to the agitator control scheme.

• Unjam only works for continuous fire
• Unjam doesn't take into account the (potentially) shaped velocity of the motor

One option is to create a ComprisedCommand with logic to handle unjamming, and have a separate unjam command which performs the motion before passing back control to whichever command was running prior, i.e. continuous or burst fire commands.