Encapsulate Field Refactoring

[mjbvz]

From microsoft/vscode#19905

Add a refactoring to encapsulate a field in a class, similar to https://msdn.microsoft.com/en-us/library/a5adyhe9.aspx:

class Foo {
    bar: string;
}

Encapsulating the bar field would change the class to:

class Foo {
    private _bar: string;

    public get bar() { return _bar; }
    public set bar(value: string) { _bar = value; }
}

[mhegazy]

Duplicate of #12417

[mjbvz]

Thanks @mhegazy

Closing as duplicate