Examples cleanup

[eigen-value]

Revamped all the examples:

• removed dependency from sys module and sys.exit() calls
• rationalization of the demo examples
• introduces some examples leveraging the arduino runtime

[gbr1]

• demo.py is wrong -> it seems to be touch_move.py
• on mpy 1.22.2 main not import demo (I don't know why)
• arduino_runtime examples must contain cleanup with alvik.stop() -> start(setup,loop, cleanup)

[eigen-value]

@gbr1
demo, touch_move and runtime examples have been amended.

Are you sure about the MP 1.22.2 issue? It seems alright to me... maybe a failed reimport?

[gbr1]

Everything is smooth :D