Simplify the shape.py points setter

[shimwell]

Currently the setter in the shape.py checks quite a lot of things about the points

https://github.com/ukaea/paramak/blob/785c3ed7304e22eac7d58bb1bdc6515fbd20b9a8/paramak/shape.py#L412-L471

This should be simplified and some of the logica can be moved into parametric shape classes that inherit from shape.

For example this could be added to the RotateStraightShape.py as a new setter that makes use of the existing points setter in Shape.py but also extends it

    @RotateMixedShape.points.setter
    def points(self, values):
        if values is not None:
            # Checks that the length of each tuple in points is 2
            for value in values:
                if len(value) != 2:
                    msg = "individual points must contain 2 coordinates {} has a \
                        length of {}".format(value, len(values[0]))
                    raise ValueError(msg) 

        super(RotateStraightShape, self.__class__).points.fset(self, values)