merge the IPath and IShape interfaces into a single structure

[tocsoft]

IPath should have

• Rectangle Bounds { get; } bounds enclosing the path
• PointInfo Distance(Vector2 point) distance from and along the path
• IPath Transform(Matrix3x2 matrix) applies the matrix transform to the path.
• int MaxIntersections { get; } Gets the maximum number intersections that a shape can have when testing a line.
• IsClosed details weather the path is closed or open
• bool Contains(Vector2 point); returns true if the point is contained within the closed version of this path
• int FindIntersections(Vector2 start, Vector2 end, Vector2[] buffer, int count, int offset); populates the buffer with all the point that intersect the line
• IPath AsClosedPath() if this is an open path closes it and returns that, otherwise it returns itself
• ImmutableArray<SimplePath> Flatten() a collection of simple paths making up this potentially complex one

Add new SimplePath struct

• ImmutableArray<Vector2> Points { get; }
• bool IsClosed { get; }

drop IShape as IPath will cover the requirements