Add constants Module
Move all the url's as a constants.
Add Timing validation
Add tag resources Validation.
Add new copy path
Merge pull request #20 from mlopez-firstfactory/master

Add the question index list
Add validation to question statistics section.
Add new constant module.
hide next question button when is only a question.
Add filter to show a level title given a number

In the new interface, given a level we display a message:
2: Easy
4: Easy/Medium
8: Medium
16: Medium/Hard
32: Hard
Fix question list when creating new question set

They are now reinitialized correctly when a new question set is
displayed to the user