popPendingEdges and Wires

[marcus7070]

Will close #621. To summarise:

• More informative exception when pendingWires or pendingEdges is empty
• Minimise code duplication
• More consistent method to pop pending Edges/Wires

I'm keeping this a draft PR until I see the test coverage, if it goes down then I'll fix that.

[marcus7070]

Just FYI, I tried two ways of solving this.

1. A single method, def getPending(edges: bool = False, wires: bool = True):
2. The two methods, popPendingEdges and popPendingWires, that you can see in this PR.

The first way needed a lot of overloads and casts to satisfy mypy. The experience has made me realise that two methods is the better solution, each method returning a single type.

[codecov]

Codecov Report

Merging #678 (d7e7812) into master (48deb19) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #678      +/-   ##
==========================================
+ Coverage   94.21%   94.27%   +0.06%     
==========================================
  Files          31       31              
  Lines        6702     6742      +40     
  Branches      726      727       +1     
==========================================
+ Hits         6314     6356      +42     
+ Misses        253      252       -1     
+ Partials      135      134       -1     

Impacted Files	Coverage Δ
cadquery/cq.py	91.02% <100.00%> (+0.22%)	⬆️
tests/test_cadquery.py	99.12% <100.00%> (+0.01%)	⬆️

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[jmwright]

Thanks @marcus7070 !