Custom board definition (MYBOARD.py) and pin aliases

Right! I had not thought of that... :)

I have 2 goals (not mutually exclusive):

1. avoid repeating ADC=D1 in every program (convenience)
   
2. avoid "burning" JS variables on simple aliases (resource optimisation)
   
   

I guess this solution addresses 1. but would there be a way to address 2. as well ?