Currently, if `device init` was ran without an application argument, we
attempted to get the application name from the current directory, given
it was a git repository.
This approach led to confusions from time to time, so now we prompt the
user to select one of it's own applications from a dropdown instead of
checking the current directory in this edge case.
Fixes: https://github.com/resin-io/resin-cli/issues/197
