Private properties of the PropertyFieldAlignPicker custom field.
We separate public & private properties to include onRender & onDispose method waited
by the PropertyFieldCustom, witout asking to the developer to add it when he's using
the PropertyFieldAlignPicker.
Instance specific context. This context is passed back to the web part in the
onRender and onDispose APIs. The web part can use this context to manage state
information.
Private properties of the PropertyFieldAlignPicker custom field. We separate public & private properties to include onRender & onDispose method waited by the PropertyFieldCustom, witout asking to the developer to add it when he's using the PropertyFieldAlignPicker.