Use GPIO BCM mode to allow use of GPIO 0 and 1

[jackw01]

rpi.GPIO is being used in BOARD mode, which doesn't allow BCM pins 0 and 1 (board pins 27 and 28) to be used. Changing it to BCM mode resolves this issue. Some existing Raspberry pi-based emulator hardware (ex: Mintypi) have buttons connected to these pins.

[mholgatem]

I used to use BCM, but it caused a lot of user related problems. This program tends to skew more towards beginners. I wouldn't be opposed to re-implementing it, but I think that what we need to do is add a flag that the user can set. We should default to board, but they can set BCM if they would prefer. You will want to check out the file usr-bin-gpionext, for creating a flag. Then in gpionext.py, you will want to add a parser argument that can receive that flag and pass it on to gpio.py. We should probably also create a function that does a check, if they have already configured using BCM or BOARD and then they change modes, it should clear the entries and prompt them to run config.

TODO:

• implement flag in usr-bin-gpionext
• default to BOARD mode
• when flag is SET/UNSET, clear entries, prompt for new configuration
• add argparse argument to gpionext.py to handle new flag
• pass new argument to gpio.py