[PROPOSAL] Format flags and fields line-by-line in traits

I'm always tired of seing traits (especially slots) as **long lines**:

```
trait slot QName(PrivateNamespace("com.my.package:MyClass"), "someVariable") flag METADATA slotid 10 type QName(PackageNamespace(""), "String") value Utf8("this is some text")
end ; trait
```

In fact, the most important data (`type` and `value`) are at the end so I have to scroll constantly. So I thought, what about having traits fields *listed in their own lines*?

```
trait slot QName(PrivateNamespace("com.my.package:MyClass"), "someVariable")
 flag METADATA
 slotid 10
 type QName(PackageNamespace(""), "String")
 value Utf8("this is some text")
end ; trait
```

You see, the same way other blocks (`class`, `body`, ...) are dumped.
This also simplifies `dumpTraits` substantially.

<sup>This PR is rather to discuss possible solutions to this problem; like the one above.</sup>