Expand all button should have recursive effect

[tscurtu]

Currently when clicking the "Expand all" (and "Collapse all", but logically moot) button in an Artifact panel, only the immediate artifact's rendering is expanded. If that Artifact's fields are also expandable, they will still be collapsed.

The effect of clicking the button should be to expand the entire contents of all children. If the user wishes to avoid expanding all, they can still still click the single-expansion chevron.