Lets you disable "duplicates" behaviour

```
yargsParser('-x 1 -x 2')
// => {x: [1, 2]}
```
```
yargsParser('-x 1 -x 2', {configuration:{'duplicate-arguments-array': false}})
// => {x: 2}
```

Lets you disable flattening of multiple array type values

```
yargsParser('-x a b -x c d', {array: ['x]})
// => {x: ['a', 'b', 'c', 'd']} // all flattened
```
```
yargsParser('-x a b -x c d', {array: ['x], configuration:{'flatten-duplicate-arrays': false}})
// => {x: [['a', 'b'], ['c', 'd']]} // multiple nested arrays
```