Feature Contribution Calculator Documentation is Vague

[rogancarr]

The documentation for the Feature Contribution Calculation Transform is rather vague. It should be updated to talk about the feature, why it is useful, and point to the corresponding example.

[rogancarr]

We need the following to resolve this issue:

1. Update the overall summary documentation to the summary/remarks/example format found here:

   machinelearning/src/Microsoft.ML.FastTree/GamTrainer.cs

   Line 36 in a570da1

   /// <summary>

   This section will talk about the FCC in general, with links to examples and implementations.
2. Each implementation, (e.g.

   machinelearning/src/Microsoft.ML.FastTree/GamTrainer.cs

   Line 670 in a570da1

   public FeatureContributionCalculator FeatureContributionClaculator => new FeatureContributionCalculator(this);

   ) will have its own summary/remarks/example section detailing how the calculation is done.