Infer T in CreateEnumerable<T> based in DataView schema

## Problem

Today, when an `IDataView` is created using `TextLoader`, there's no need to create classes that define the schema.

```csharp
var cols = new []
{
new TextLoader.Column(name: "Text",dataKind:DataKind.String,index:47),
new TextLoader.Column(
name: "Categorical",
dataKind: DataKind.String,
source: new TextLoader.Range[] {
new TextLoader.Range(19),
new TextLoader.Range(20),
new TextLoader.Range(21),
new TextLoader.Range(50),
new TextLoader.Range(59),
new TextLoader.Range(71),
new TextLoader.Range(83)}),
new TextLoader.Column(name:"Label",dataKind:DataKind.String,2)
};

var dataLoader = ctx.Data.CreateTextLoader(columns:cols);
var idv = dataLoader.Load(path);
```

However, if I want to export the `IDataView` as an `IEnumerable`, I can't because I need to explicitly provide the type of `IEnumerable`. If no classes have been created, I now need to go and create a new class just to export to an `IEnumerable`.

## Proposed solution

Just like `LoadFromEnumerable` is able to infer and create an IDataView from `IEnumerable`, `CreateEnumerable` should be able to infer `T` based on the DataView schema or bind to an object at runtime using `dynamic`.

```csharp
ctx.Data.CreateEnumerable(idv,reuseRowObject:false,ignoreMissingColumns:false)
```

or

```csharp
ctx.Data.CreateEnumerable(idv,reuseRowObject:false,ignoreMissingColumns:false)
```