ShapelyGeography: integrate shapely and geoalchemy2

shapely_geo.py

class ShapelyGeography(Geography):

    def result_processor(self, dialect, coltype):
        super_process = super().result_processor(dialect, coltype)

        def process(value):
            value = super_process(value)
            if value is not None:
                return to_shape(value)
        return process

    def bind_processor(self, dialect):
        super_process = super().bind_processor(dialect)

        def process(bindvalue):
            if isinstance(bindvalue, BaseGeometry):
                bindvalue = bindvalue.wkt
            return super_process(bindvalue)
        return process