Add requested output from getter/setter to the context object

[rglover]

This would come in handy if you want to control what data you retrieve inside of the getter/setter (instead of just letting Joystick filter it out after the fact).

[rglover]

So it's clear, this is literally saying take the output field passed with a client-side get() or set() call and add it to the context object on the getter/setter definition.