Triple production

Here is a first way to obtain triples, please notice that:
  - you can try it with demo5.py. Enter `python3 demo5.py` and then your question
  - it's only designed for `who`questions (but it can work for other types of questions)
  - only the most common dependency relations have been taken in account
  - the biggest problem is about `amod` : 
      - sometimes the 2 nodes must be merged
      - otherwise, the two node are for example `first` + `president`, or `tallest` + `man`, or `largest` + `city`. What triples should we produce ? `(?,first,president)`, `(?,tallest,man)` and `(?,largest,city)` ?