Ignore Columns ColumnInference

When using `InferColumns`, there is now way to specify which columns to exclude.

```csharp
// Define data path
var dataPath = Path.GetFullPath(@"../Data/issues_train.tsv");

// Infer column information
ColumnInferenceResults columnInference =
ctx.Auto().InferColumns(dataPath, separatorChar: '\t', labelColumnName: "Area", groupColumns: false);
```

That means that you have to do it manually.

```csharp
var columnsToExclude = new[]{"ID","Title"};

columnInference.TextLoaderOptions.Columns =
columnInference.TextLoaderOptions.Columns
.Where(col => !columnsToExclude.Contains(col.Name)).ToArray();

columnInference.ColumnInformation.NumericColumnNames.Remove("ID");
columnInference.ColumnInformation.TextColumnNames.Remove("Title");
```

Since the TextLoaderOptions and ColumnInformation are used downstream

```csharp
// Create text loader
TextLoader loader = ctx.Data.CreateTextLoader(columnInference.TextLoaderOptions);

// Load data into IDataView
IDataView data = loader.Load(dataPath);

SweepablePipeline pipeline =
ctx.Auto().Featurizer(data, columnInformation: columnInference.ColumnInformation)
.Append(ctx.Transforms.Conversion.MapValueToKey(columnInference.ColumnInformation.LabelColumnName))
.Append(ctx.Auto().MultiClassification(labelColumnName: columnInference.ColumnInformation.LabelColumnName))
.Append(ctx.Transforms.Conversion.MapKeyToValue("PredictedLabel"));
```

In the InferColumns API, it might be the best place to set this value