Arm homing function

[jkleiber]

Summary
The arm uses a relative encoder to determine its position. Thus, we need a homing command that runs whenever the robot gets enabled to reset that encoder position to 0. This will be determined by current limits, so current limits at the hard stops need to be understood as well.

Work Scope

• Set the current limits correctly for running the arm into the hard stops
• Develop a command for homing the arm. This should be as simple as creating a new ArmMode called Home. When in Home mode during periodic(), the arm should run at a fixed power in the upward direction (shoot/idle position) until a current limit is hit. Then the encoder should reset and the arm should go back into Idle mode.
• Make a button binding for the arm homing command (in case it loses its home in match)
• Run the arm homing command in enabledInit (or teleopInit and autoInit if this is a function that doesn't exist)

Verification

• Demonstrate that the arm homes in teleop