Support clip-to-frame (clipRectangle) and clipAngle projection options

[Fil]

• clipAngle works on the input stream, and only for spherical data. Maybe limit this option to the named azimuthal projections.
• clipRectangle works on the output stream, after rescaling (since we'll want to clip to the frame), and before simplification (projection fixed-precision option? #1143). It could be applied to any projection (with a special case for the null projection?).