add LineSegment type

[schillic]

No description provided.

[mforets]

in 2d? it could be implemented by holding the pair of points p1, p2, no?

[schillic]

This is exactly the idea. I need this for the intersection of polygons. So I also need the intersection of line segments, which is why I do not want to use VPolygon here but introduce an extra type.

[mforets]

alright! what we can do now is:

julia> p1, p2 = zeros(2), ones(2);
julia> plot(CH(Singleton(p1), Singleton(p2)), .1)

or VPolygon([p1, p2]). for the new type it could plot the extreme points.