Maintenance refactor of the GDAL (OGR) ctypes interface. Changes include:

* All C API method explictly called from their prototype module, no longer imported via *.
* Applied DRY to C pointer management, classes that do so subclass from `GDALBase`.
* `OGRGeometry`: Added `from_bbox` class method (patch from Christopher Schmidt) and `kml` property.
* `SpatialReference`: Now initialize with `SetFromUserInput` (initialization is now more simple and flexible); removed duplicate methods.
* `Envelope`: Added `expand_to_include` method and now allow same coordinates for lower left and upper right points.  Thanks to Paul Smith for tickets and patches.
* `OGRGeomType`: Now treat OGC 'Geometry' type as 'Unknown'.

Fixed #9855, #10368, #10380.  Refs #9806.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@9985 bcc190cf-cafb-0310-a4f2-bffc1f526a37