Port sequence confidence changes

[Enkidu93]

Many changes were not relevant to Machine (C#). My only question: For the TranslationEngines that create translation results in Machine, should I just provide a dummy -1.0 value for the sequence confidence or should I combine the individual confidences in some way to create the sequence confidence (e.g. geometric mean)?

Fixes #396.

Port changes from sillsdev/machine.py#279.

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This change is 

[codecov-commenter]

Codecov Report

❌ Patch coverage is 55.55556% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.99%. Comparing base (cd06553) to head (c364fd4).

Files with missing lines	Patch %	Lines
...SIL.Machine/Translation/HybridTranslationEngine.cs	0.00%	1 Missing ⚠️
...c/SIL.Machine/Translation/TranslationExtensions.cs	0.00%	1 Missing ⚠️
src/SIL.Machine/Translation/TranslationResult.cs	66.66%	1 Missing ⚠️
...IL.Machine/Translation/TranslationResultBuilder.cs	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #400      +/-   ##
==========================================
- Coverage   73.00%   72.99%   -0.01%     
==========================================
  Files         439      439              
  Lines       36672    36681       +9     
  Branches     5036     5036              
==========================================
+ Hits        26772    26777       +5     
- Misses       8785     8789       +4     
  Partials     1115     1115              

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[ddaspit]

@ddaspit reviewed 5 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on Enkidu93).

[Enkidu93]

@ddaspit, just wanted to make sure you saw my question above. I'm assuming you're OK with the -1.0 default then?

@Enkidu93 made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on Enkidu93).

[ddaspit]

I think using the geometric mean of the word confidences would be good.

@ddaspit made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on Enkidu93).