Standardize i18n for martor

[int-y1]

most templates use {{ _('foo') }} for i18n. apply this to martor.

this shouldn't change the editor's behaviour

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 47.70%. Comparing base (fd7fb05) to head (7eff0ad).
Report is 67 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2403      +/-   ##
==========================================
+ Coverage   46.76%   47.70%   +0.93%     
==========================================
  Files         251      259       +8     
  Lines       13317    13719     +402     
==========================================
+ Hits         6228     6544     +316     
- Misses       7089     7175      +86     

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[quantum5]

most templates use {{ _('foo') }} for i18n. apply this to martor.

"Most" templates are Jinja2. I can't tell if these martor templates are being loaded as Jinja2 or plain Django templates.

this shouldn't change the editor's behaviour

If it's loaded as Django, very bad things will happen.