GlobalDrawer: Port away from modelData

Replaces modelData and hasOwnProperty spaghetti with typed checks and
self-descriptively named shorthand properties.

Fixes inconsistencies between visibility bindings on expanded and
non-expanded representations of ActionDelegate: non-expanded variant
lacked "children.length" check, and the expanded variant forgot to
check whether an action is visible at all.

Cleaned up some qualified properties access; moved ToolTip out of
superfluous data list.