Remove [prod : dev] keys from output, and allow nested array appending.

This set of patches removes "prod : dev" declarations from output, leaving only the full "prod" and "dev" options.

The second commit allows for nested array appending. Allowing something like the following.

```
nested.a[] = a
nested.a[] = b
nested.a[] = 1
```

which returns

```
array(
  'nested' => array(
    'a' => array('a', 'b', 1),
  ),
)
```