Fully closed shelling

[adam-urbanczyk]

This will solve #393 . I was motivated by the discussion on our google group and it is rather small fix. Now one can create hollow models easily:

b = cq.Wokrplane().box(1,1,1).shell(-0.1)

[codecov]

Codecov Report

Merging #394 into master will increase coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #394      +/-   ##
==========================================
+ Coverage   93.38%   93.44%   +0.05%     
==========================================
  Files          19       19              
  Lines        4976     4989      +13     
  Branches      508      509       +1     
==========================================
+ Hits         4647     4662      +15     
+ Misses        206      205       -1     
+ Partials      123      122       -1     

Impacted Files	Coverage Δ
cadquery/cq.py	87.70% <ø> (+0.19%)	⬆️
cadquery/occ_impl/shapes.py	90.24% <100.00%> (+0.10%)	⬆️
tests/test_cadquery.py	98.94% <100.00%> (+<0.01%)	⬆️

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[jmwright]

Looks good @adam-urbanczyk thanks!

[adam-urbanczyk]

Merging.