Add support for multiple game controllers.

[AnthonyScalise]

The user should be able to define the number of game controllers using the C++ library creating instances of the gamePad structure. The library should specify the number of game controllers in the initialization JSON message. The client-side JS should be able to take the number of controllers and create multiple gamePad widgets to specification. The JS should be able to update the game controller data in the dashboard data array to be sent back to the host. Lastly, the C++ library should then be able to allow public access to gamepad data through the gamePadButton and gamePadAxes functions given the game controller instance number.