refactored geo primitives, added octehedron

src/mol-geo/primitive/box.ts

src/mol-geo/primitive/cylinder.ts

src/mol-geo/primitive/icosahedron.ts

src/mol-geo/primitive/octahedron.ts

src/mol-geo/primitive/plane.ts

src/mol-geo/primitive/polyhedron.ts

src/mol-geo/primitive/primitive.ts

src/mol-geo/primitive/sheet.ts

src/mol-geo/primitive/sphere.ts

src/mol-geo/primitive/star.ts

src/mol-geo/primitive/tube.ts

src/mol-geo/primitive/wedge.ts

...presentation/structure/visual/carbohydrate-symbol-mesh.ts

...o/representation/structure/visual/polymer-gap-cylinder.ts

src/mol-geo/representation/structure/visual/util/element.ts

src/mol-geo/shape/mesh-builder.ts

src/mol-math/linear-algebra/3d/vec3.ts