Add enlarge method to BoundBox

[AshtonOhms]

Surfaces Bnd_Box's Enlarge in the BoundBox class.

[codecov]

Codecov Report

Merging #1356 (fe8bddf) into master (b96eb8a) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head fe8bddf differs from pull request most recent head de3f528. Consider uploading reports for the commit de3f528 to get more accurate results

@@           Coverage Diff           @@
##           master    #1356   +/-   ##
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  Coverage   94.16%   94.16%           
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  Files          26       26           
  Lines        5584     5590    +6     
  Branches      954      954           
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+ Hits         5258     5264    +6     
  Misses        194      194           
  Partials      132      132           

Impacted Files	Coverage Δ
cadquery/occ_impl/geom.py	99.59% <100.00%> (+<0.01%)	⬆️

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[adam-urbanczyk]

Thanks, could you first explain why is this needed?

[AshtonOhms]

This is useful for detecting when geometry is on the edge of (or just outside of) the original, un-enlarged bounding box.

My particular use case is a custom Selector for geometry within a BoundBox using isInside(). I need to enlarge the box by a small margin, otherwise the Selector misses geometry on the edges. Apart from this niche case, I think this is generally helpful for those edge cases with isInside().

[jmwright]

Looks good to me. I've experimented with automatically finding interreference and excessive gaps between components in an assembly before, and this could be useful for that. Thanks @AshtonOhms