Dockerfile, remove ENTRYPOINT, fix dependencies, OCR-D/spec#130

[kba]

No description provided.

[codecov]

Codecov Report

Merging #87 into edge will increase coverage by 0.28%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             edge      #87      +/-   ##
==========================================
+ Coverage   46.53%   46.82%   +0.28%     
==========================================
  Files           8        8              
  Lines         692      692              
  Branches      129      129              
==========================================
+ Hits          322      324       +2     
+ Misses        338      337       -1     
+ Partials       32       31       -1

Impacted Files	Coverage Δ
ocrd_tesserocr/recognize.py	53.5% <0%> (+1%)	⬆️

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