Update output to make the root object an overview with results contained inside

[gregsdennis]

This makes progress toward some of what is discussed in #1065.

Basically, we need a place to include metadata about an evaluation. This PR wraps the existing output in a root node that can contains any such metadata.

(As a side effect, it creates a purpose for the root object in the case of the "list" format, which could have just been an array before.)

[gregsdennis]

Re-reading through the issue, it seems that dialect should be part of the output unit itself rather than the summary. Still... I think the summary root node is a good addition.

[jdesrosiers]

Re-reading through the issue, it seems that dialect should be part of the output unit itself rather than the summary. Still... I think the summary root node is a good addition.

I agree that dialect should be part of the output unit. I'm not sure putting it in the summary makes sense. Validation can include references to other schema resources that use a different dialect. So, dialect in the summary is only telling you the dialect of the root schema. Maybe that's ok, but it might be misleading if the evaluation includes multiple dialects.

[gregsdennis]

I'll remove dialect from this PR and do another one for that then.

I know we had a discussion somewhere on having some more "global" details in the root node, though...

[jdesrosiers]

You missed a couple places removing dialect, but otherwise, this looks good to me.