methods
While unused for now, this gives us flexibility in future to specify
additional useful contextual information about how a callout should
be rendered without breaking API (e.g. label text alignment, label
font settings, etc)
And replace labeling engine dialog "Draw text as outlines" checkbox with a combobox
presenting the choice of always rendering as outlines OR text.
(This will allow us to easily add additional methods in future, e.g. potentially
a "Render as text wherever possible" setting, for defaulting to text objects
whenever it doesn't impact the rendering quality to do so)
