When the demo is running, it will detect one biggest face at real time. Once the face is
detected, you can click keyboards on the right of GUI to input the new person's name. Then,
click 'Add new person' to add the face to data set.
In brief,
1. Detect face.
2. Input new person's name.
3. Click 'Add new person'.
Note: Once new faces are added, it will create a folder named 'data' in current directory. If you
want to remove the new face from the data set, just delete it in 'data'.