Add remaining geometry primitives to Draw API

[mitchmindtree]

• line Add a Draw::line method along with custom line builders to Drawing #98 Add cap module to line submodule #157
• polygon Implement draw.polygon() API #148
• mesh Add draw.mesh() API. Add simple_mesh.rs example. Add IntoVertex trait. #154
• polyline
• cuboid

Removed in favour of mesh

• tri_iter
• vertex_indices

[mitchmindtree]

There are many more primitives that could be added (especially 3D), but going to close this as it's outdated and we're better off with individual issues per desired primitive.