Added lower limit switch to Lifter subsystem.

The limit switch will be used to stop the lifter when it reaches the lower
limit.
Reversed Conveyor direction constants.

The conveyor now rotates in the correct direction.
Removed Auger non-interruptible state.

The auger can now be interrupted. This is to prevent the augers from
over-rotating upwards.
Removed Collector to limit commands and added emergency Auger-stop button.

The collector (temporarily) does not have limit switches.
Middle-Left button now stops the Auger when in an Emergency.
Fixed Channel constants and added Lifter lower limit switch constant.
Overloaded two methods and fixed stop() method in Zed.

disabledInit() and disabledPeriodic() are now overloaded and the safety
stop functions in stop() method use the individual DrivetrainStrafe and
DrivetrainRotation systems instead of the wrapping Drivetrain class.
Remove PID control from shooter CANJaguars.

The shooter has no encoders mounted and is now controlled in PercentVBus
mode, similar to PWM values.
Add speed multiplier to GamepadDriveStrafeCommand.

It is now possible to scale the magnitude of the robot's strafing.
Add robot startup message to Zed.

The robot now prints a message after it is initialized to indicate
that it has started up.