Add annulus implicit function and associated representation/widget

The new vtkAnnulus implicit function represents an infinite annulus (two concentric circles). It exposes getters and setters for its axis, origin, and inner/outer radii parameters. Changing those will automatically update the base vtkImplicitFunction's transform.

The new vtkAnnulus has a widget representation. Users can manipulate the function through widget controls:

• Rotate through the axis handle
• Translate through the center handle
• Scale through the outline handle
• Adjust inner/outer radii through the cone edges handles

Its underlying annulus can be used in any filter relying on implicit functions (i.e. Clip, Slice).