[C2] Extend adaptative tests to all questions

[ywarnier]

In C1, the c_quiz_answer table holds a "destination" field that allows the teacher to select a destination (in the adaptative mode) for each selected answer.

This brings an issue, in that the same question cannot be used in 2 different adaptative tests (because the answer is global and not for the specific context of one adaptative test).

It also prevents us to define destinations for anything else than questions of type unique answers or delineation.

However, removing the destination field from c_quiz_answer and moving it to c_quiz_rel_question will remove the level of detail that answer.destination gave us, which was to define a destination per selected answer. This is probably a temporary loss. We can add the feature again later on, but to move fast we have to loose this capability and data for now (upon migration, adaptative tests will have to be re-edited).

h2. To do list

• Create the c_quiz_rel_question.destination field as a text field (it will hold a JSON array like { sucess: '/main/exercise/35/q/4', failure: '/main/lp/134'}. The field can be empty to start with). Create the migration, fixtures and entities for this if necessary.
• Remove the c_quiz_answer.destination field through a migration (and modify the entity).
• Create additional fields at the end of the question edition field, that only appear (like the previous destination field for each answer) in the context of an adaptative test. Use the same syntax to save possible destinations (including "repeat" and other particular choices), but only for "Success" or "Failure", "Success" being considered as obtaining the maximum score for that question.
• Remove the code related to destination on specific answers (including the forms in adaptative mode).

[christianbeeznest]

Refactored adaptive test navigation logic. Destinations on success or failure are now defined per question (c_quiz_rel_question.destination) instead of per answer. Removed all references to c_quiz_answer.destination. Updated navigation flow and link rendering accordingly.

[ywarnier]

When I set the following:

Question id	Success destination	Failure destination
1	3	2
2	1	repeat
3	end test	repeat

If I enter the test and answer Q1 correctly, I can get to Q3 (fine).
However, if I enter the test and answer Q1 incorrectly, I move to Q2 (also fine), then I answer Q2 correctly and get back to Q1 (also fine). But when I then answer correctly to Q1, I am sent back to Q2 (incorrect, I should move to Q3).

This is not blocking for the alpha 2 release, but it is important to fix it.
The rest works fine but it will also be necessary to visually add those other question types now (the ones that are not open questions). Closing and opening new issue to finish post-alpha.