ask for example model file in init flow about graphback

[ankitjena]

@wtrocki Should we create custom model too taking input from user, just the filename, user will enter the details later on.

[wtrocki]

I think input from user makes this command go for long. Usually you would probably be better to have project as fast as possible and then edit stuff in your fav ide. If someone says no in cmd we should be creating empty file maybe or file with example that is commented out will be even better