Improve HW_Wire styles

The EdgeMapping is specified from modules to pins.
Keep only the target arrow for links to input pins and the source 
arrow for links from output pins.
When a sensor is linked to an instruction, dispay its status

If a Led:on is displayed on the diagram, if we link a push button to
it, the edge label is off: when the user will push the button, 
it will disable the led.