ADDED arc, circle and rectangle shapes for schematic. Shapes support
line styles and fill colors.
CHANGED sheet background color in Edit Text & Graphics Properties to
fill color (and it now affects shapes).
Pushed STROKE_PARAMS down into common and moved all shapes to using it
for stroke descriptions.
Introduce the concept of a DRC_PROVIDER which allows
to separate the various DRC functions to their own
areas. This allows, amongst other things, a slimmer core
DRC class, and allows DRC functions to be separately testable.
The courtyard DRCs (overlap, missing and malformed)
are the first victims, so instrumentation can be added to this function.
Add some unit tests on this DRC function, as well a few re-usable PCB-based
utility functions in a library (qa_pcbnew_utils) that could be shared between
unit tests and other utilities.
