Could not change a question type back to Choice #2241

This was due to the list of choice which was wrongly pre-filled with an
empty choice instead of loading actual list of choice from server
Ignore empty choices when saving #2241

It used to crash when saving a question with an empty choice. For
instance if we hit "Add choice" button and left it empty. We now
completely ignore empty choices.
Fix print from the root of the current section that only was displaying current question instead of all section
Implements required fields compulsory backoffice side avoiding conflits when changing from question choice #2211
Set thematic and parts fields optionnal

These fields more advances and dont interpret correctly ng-required that needs to be dynamic
Use standard .gz extension instead of .gzip
Remove obsolete code
Introduce formula support during regression computing #2288

In order to accurately reproduce computing as seen in tab "Estimates"
of Excel files, we had to introduce an optional usage of formula
when computing regression values. This allow us to introduce dependecies
on other filters as seen in Excel files (eg: "Other improved")
Remove comment debug zone in questionnaire
Remove comment debug zone in questionnaire
Merge branch 'develop'