Run test-oldest on the minimal required version of Orange

[janezd]

Issue

• Run test-oldest on the minimal required version of Orange
• Remove unused imports from setup.py. They were added when trying to implement multilingual build and we forgot to remove them.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.44%. Comparing base (c11ed3e) to head (05b629c).
Report is 15 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #248      +/-   ##
==========================================
+ Coverage   72.97%   73.44%   +0.46%     
==========================================
  Files          18       18              
  Lines        2875     2922      +47     
  Branches      402      346      -56     
==========================================
+ Hits         2098     2146      +48     
+ Misses        664      663       -1     
  Partials      113      113              

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