that these are automatically respected whenever the format is
rendered using QgsTextRenderer
This is done transparently to the caller - so by porting away
from the raw QPainter text apis to use QgsTextRenderer instead,
then they immediately gain the ability to use data defined
properties in their text formats.
Allows for rendering a marker symbol in the background of labels
(complementing the existing shapes/SVG choices). This allows use
of QGIS marker symbology as a background symbol behind labels (e.g.
for highway shield labels)
Moves all the drawing code out of labeling into a new class
which just handles rendering text. This allows other parts
of the code to utilise all the advanced formatting options
that labeling supports, eg rendering text with shadows,
buffers and backgrounds.
