Fix operations with different numbers of properties

[elalish]

Fixes #479

There were two related bugs here: one in the Boolean and one in Compose. Compose was not handling properties at all (oops!), while the Boolean was assuming both inputs had the same number of properties. I added several tests inspired by the linked issue, but made them quite a bit more comprehensive.

[codecov]

Codecov Report

Patch coverage: 93.61% and project coverage change: +0.32 🎉

Comparison is base (dd3445d) 89.94% compared to head (0198042) 90.27%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #480      +/-   ##
==========================================
+ Coverage   89.94%   90.27%   +0.32%     
==========================================
  Files          35       35              
  Lines        4286     4318      +32     
==========================================
+ Hits         3855     3898      +43     
+ Misses        431      420      -11     

Impacted Files	Coverage Δ
src/manifold/src/csg_tree.cpp	91.40% <89.28%> (-0.42%)	⬇️
src/manifold/src/boolean_result.cpp	97.46% <100.00%> (+0.04%)	⬆️

... and 2 files with indirect coverage changes

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[stephomi]

Thanks!