sort factor levels

[Felixmil]

Sorry for the "double" PR but I think it is better if the factors levels are sorted.

[codecov-commenter]

Codecov Report

Attention: 9 lines in your changes are missing coverage. Please review.

Comparison is base (570fc8a) 60.58% compared to head (e3607ce) 60.64%.
Report is 8 commits behind head on master.

❗ Current head e3607ce differs from pull request most recent head a788e63. Consider uploading reports for the commit a788e63 to get more accurate results

Files	Patch %	Lines
R/edit-data-utils.R	0.00%	4 Missing ⚠️
R/import-file.R	71.42%	4 Missing ⚠️
R/utils.R	66.66%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master      #85      +/-   ##
==========================================
+ Coverage   60.58%   60.64%   +0.06%     
==========================================
  Files          17       17              
  Lines        2456     2470      +14     
==========================================
+ Hits         1488     1498      +10     
- Misses        968      972       +4     

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[pvictor]

No problem, thanks!