[ENHANCEMENT] Survey prototype inside pltp activity

[nborie]

The goal of this issue is to add a small survey mode inside pltp.

If and exercice is prefixed by survey_, thus

• The survey_xxxxx.pl is therefore considered as a survey.
• The exercice user form MUST have finite number of questions.
• Each question inside the form MUST have finite number of possibles answers.
• The grade is 100 whatever is the answer (not an exercice but a survey...)
• Only the last answer of each user is considered

All the previous spec should be more reformalted within the coming prototype.

The effect will be therefore :

• survey_ exercice do not enter regular dashboard.
• Following the results are public or not, student and teacher dashboard become histogram of occurences of possible answer.
• The CSV gathering result will separate the survey results.

Globals variables and their défaut value (to be continued) :

allow_change_answer = False
allow_student_dashboard = True
graphic_type = "histogram"

Use cases :

• Visualisation of multiples choices survey
• Peer evaluations with evaluation grids

[nimdanor]

A faire comme activité platon.

[nborie]

Back du dashboard :
https://github.com/PremierLangage/premierlangage/blob/master/apps/activity/activity_type/pltp.py

front de la vue :
https://github.com/PremierLangage/premierlangage/blob/master/apps/activity/templates/activity/activity_type/pltp/teacher_dashboard.html