Modify VDOM Spec

[Archmonger]

Current Situation

There are a few awkward designs of the current VDOM spec. We might want to push for a handful of changes.

Proposed Actions

Things that might require changes:

• The key attribute is no longer needed as of this PR: Ensures key is properly propagated to importedElements #1271
• The VDOM spec currently uses camelCase for keys, but we really should be writing this from the perspective of Python, which uses snake_case.