Add MetadataPanel

Use it to show a model's owner and creation date.
Rename ModelListJSO#getModelId to #getId

Because terser = better.
Return ModelListJSO from DataManager#findModel

Returning the JSO is much more convenient than returning just the model
name or id.
Show model metadata in OpenDialogBox

Display the owner and creation date of the currently selected model in
the OpenDialogBox.