Rename types inside MLContext as Catalogs

[TomFinley]

We had an idea in #949 to have "context" objects that enabled the easy and convenient creation of training algorithms. We eventually came to like this idea so much that it expanded considerably, until we came to think it actually a good idea that most components (whether trainers or not) could work through this object, to the point where eventually in in #1098, there was a "master" context, of which the formerly independent contexts became properties of that master context.

The newer things that were added were then called "catalogs," for example:

machinelearning/src/Microsoft.ML.Data/MLContext.cs

Line 47 in cb37c7e

public TransformsCatalog Transforms { get; }

machinelearning/src/Microsoft.ML.Data/MLContext.cs

Line 52 in cb37c7e

public ModelOperationsCatalog Model { get; }

However the old objects retained the type names they had back when they were independent.

machinelearning/src/Microsoft.ML.Data/MLContext.cs

Line 25 in cb37c7e

public BinaryClassificationContext BinaryClassification { get; }

We ought to probably standardize the name of these things as being "catalogs." E.g., things in here with the type name suffix Context should change that to Catalog, things that are catalogs but aren't named that yet (DataOperations) should be standardized as well.

[mareklinka]

Would the rename also apply to base classes? E.g. TrainContextBase in public sealed class BinaryClassificationCatalog : TrainContextBase? I would think that yes, those should be made consistent as well, just want to make sure.

The same thing then of course applies to method parameters (ctx -> catalog) and any mention in the documentation comments.

[TomFinley]

Hi @mareklinka , good question, what you say makes sense to me, yes. I'd suppose most objects of this sort whether the abstract classes or the leaf classes would be named catalog instead of context.