TODO

   1 Replace underscore by lodash (or better: ES6)
   2 Replace socket.io by Websockets ( https://www.npmjs.com/package/websocket )
   3
   4 time per question (in mode "one question at a time" from server...)
   5 compute grades after exam (in teacher's view)
   6 factorize redundant code in course.js, monitor.js and (TOWRITE) grade.js
   7   (showing students list + grades or papers)
   8 monitoring: main teacher should not be asked for pwd, and button "send feedback" hidden for others
   9
  10 -----
  11
  12 TODO: format général TXT: (compilé en JSON)
  13
  14 10 (time)
  15 1 (fixed)
  16 Introduction (multiline, from third line ; \n --> <br>)
  17
  18 [Intro q1, multiline]
  19
  20 q1 txt
  21
  22 answer q1 (multiline txt)
  23
  24 q2 intro (multiline)
  25
  26   q2.1 [intro optional]
  27
  28     q2.1 txt
  29
  30     q2.1 options:
  31     + good
  32     - bad
  33     - bad ...etc
  34
  35     answer (integer array, one line)
  36
  37   q2.2 [intro optional]
  38
  39     q2.2 txt
  40
  41     answer (html multiline)
  42
  43 Conclusion (last block)
  44
  45 =====
  46
  47 Seems that GUI would be easier, then summary in YAML file + parse from YAML