GetNormalizerModelParameters would be nice to accept name of column instead of index

```
var normalize = mlContext.Transforms.NormalizeMinMax(new InputOutputColumnPair[] { new InputOutputColumnPair("ANorm", "A"), new InputOutputColumnPair("BNorm", "B") }, fixZero: false);
```

So right now in order to get parameters for `BNorm` column I need to do this:
```
(normalizeTransform.GetNormalizerModelParameters(1) as Microsoft.ML.Transforms.NormalizingTransformer.AffineNormalizerModelParameters>);
```

Can we have another function which would accept name of column instead of index in `InputOutputColumnPair` array?

```
(normalizeTransform.GetNormalizerModelParameters("BNorm") as Microsoft.ML.Transforms.NormalizingTransformer.AffineNormalizerModelParameters>);
```