Show editing interface for Falsey ListProperty members.
Add VariableListProperty to properties.pxd
Use ObservableList to store VariableListProperty values.

Allow editing VariableListProperty values in the inspector.
Tweak VariableListProperty example formatting.
Merge branch 'master' into inspector_properties
Merge branch 'master' into inspector_properties
Merge pull request #1365 from Ian-Foote/inspector_properties

Allow VariableListProperty to be edited in the inspector.