add configurable controls

[RobDavenport]

Resolves #1
Resolves #7

This will also lead the way to do: #86 next

[RobDavenport]

default input json looks something like this:

[
  {
    "H": "RightXPositive",
    "Left": "Left",
    "I": "ButtonB",
    "K": "ButtonD",
    "U": "ButtonA",
    "Y": "RightTrigger",
    "S": "LeftYNegative",
    "A": "LeftXNegative",
    "J": "ButtonC",
    "Q": "LeftTrigger",
    "W": "LeftYPositive",
    "T": "RightYPositive",
    "Up": "Up",
    "F": "RightXNegative",
    "X": "LeftStick",
    "Down": "Down",
    "Key6": "Select",
    "R": "RightShoulder",
    "E": "LeftShoulder",
    "B": "RightStick",
    "Right": "Right",
    "D": "LeftXPositive",
    "G": "RightYNegative",
    "Key5": "Start"
  }
]