Improvement to nested output

Given this dictionary:

```json
{
  "adict": {"a": 1, "b": 2, "c": 3}, 
  "alist": [{"a": 1, "b": 2, "c": 3}, [1, 2, 3], "abc"], 
  "astring": "abc"
}
```

``salt.output.nested`` currently prints:

```
adict:
    ----------
    a:
        1
    b:
        2
    c:
        3
alist:
    ----------
    - a:
        1
    - b:
        2
    - c:
        3
    |_
      - 1
      - 2
      - 3
    - abc
astring:
    abc
```
Where the dictionary within the list looks very much like a list and not much like a dictionary.

This merge request changes the output to:

```
adict:
    ----------
    a:
        1
    b:
        2
    c:
        3
alist:
    |_
      ----------
      a:
          1
      b:
          2
      c:
          3
    |_
      - 1
      - 2
      - 3
    - abc
astring:
    abc
```

I believe this is more uniform behavior.