Don't make labels for every component on startup

@mcflugen points out that with 200 components, this could be
overwhelming. Instead, only make a label for the component that's
selected as the driver. The label will persist in the session even if
the driver is deleted.
Add an eponymous label when a new user signs in

The label = the user's email address.
Add LabelJSO class to describe return from tag/list

Also add a test JSON file to read.
On login, retrieve and store the list of labels

This includes all labels owned by the user, as well as all public
labels. (I might revisit and remove the latter.)
Add "selected" variable, with getter/setter, to LabelJSO