Hopper: refine commands and update button bindings

[derickson2402]

The commands for the Hopper subsystem, as well as the safety override mode, need to be polished up and bound to buttons on the driver controller. The following need to be set up:

• Unload sequence - Go up on button hold, expel balls for 2 seconds on release (Y button?)
• Load - Go down and run intake (A button?)
• Default - Not sure yet what this needs to be
• Manual - Use joystick for the lift, and buttons for the intake

Give each command some polishing, and check that the buttons are configured correctly.

[derickson2402]

See #24 for info on the default command and the manual command