Allow more sensitive button presses

[likethemammal]

The way the button pressed is written now, the button on fires if it was pressed completely (to value 1.0) and then released. This should be given more lenience.

There should also be a way of telling if a button is being held, and if multiple buttons are being pressed/held.

• Pressed
  • On keyup, if not held
• Held
  • On keydown, after 50ms delay

[likethemammal]

The trouble with this, is that allowing presses below the value of 1 means controllers with "noisy" buttons will count as presses. By noisy buttons, I mean when not being held, the button's pressed value will fluctuate between 0 and 1. This is likely due to the triggers in the buttons becoming inaccurate over time.

Can't think of a compromise at the moment..