geometric constructions

• sphere_through_points (in any dimension N for up to N+1 points, use Moebius lift for this) #687 (closed)
• orthogonal_sphere (get orthogonal sphere to a given number of spheres, take polar complement in Moebius lift) #688
• radical_hyperplane (radical_line in 2D)
• perpendicular_bisector
• angle_bisector
• orthogonal_subspace (to a number of subspaces, the orthogonal subspace can be made more unique by intersecting all given subspaces)
• midpoint
• center_of_mass as alias for midpoint
• tangent_cone (for a number of spheres, use Laguerre lift) are our spheres oriented?
• tangential_distance (for spheres)
• sphere_tangent_to_hyperplanes (use Laguerre lift)
• distance (for arbitary subspaces) should this be the d method?
• volume needs some discussion: "volume of three points in 3D could return the area or 0"; open zulip discussion on this!
• corner_angle
• corner_angle_signed
• focii (of conic), focal_curves, ... (where should this go?)