Add a deadzone to gamepad input

[whymarrh]

Currently the gamepad input is raw and without a deadzone. Apparently this is "literally unusable."

Possible deadzone implementations include axial (independent axes) or radial (circular):

You will generally want to use IndependentAxes mode for things where the X and Y stick positions control unrelated game values. For instance steering a car is independent of accelerating and braking, or moving up and down through a menu is independent of moving left and right. The Circular mode works better for things where the stick input is used to choose a location on a 2D plane, such as aiming a weapon or moving the character in a Mario64 style platformer. — Gamepads suck

[whymarrh]

Refs: Gamepads suck and Doing Thumbstick Dead Zones Right

[arandell93]

in a Mario64 style platformer

Is it too late to turn the boat project into a Mario64 style platformer?