- Parameterized geometry (e.g. BoxGeometry) should not clone the base
properties of Geometry.
- CubeTexture: Clone is parameterless.

Provide a clone method to the specialized geometries in
src/extras/geometry, otherwise:
- the `.parameters` are not copied
- the `.type` of the clone is "Geometry" or "BufferGeometry"
- the cloned object is not an instance of the initial type. It loses its
specialization and becomes a plain `Geometry` or `BufferGeometry`.

Class deriving from `PolyhedronGeometry` defined  `this.parameters` all
over the place. Standardize to defining the `.type` and `.parameters`
after the `PolyhedronGeometry` constructor is called.

Also fix prototype inheritance chain for classes deriving from
`PolyhedronGeometry`.

- WebGLMultipleRenderers: Use Geometry instead of BufferGeometry
- index.html: add "webgl_multiple_renderers" again
- Misc. fixes to please closure compiler (unused var).

Replace `geom.offsets.push` / `geom.drawcalls.push` with
`geom.addDrawCall()` everywhere.

The definition of `BufferAttribute.length` has changed since r71 (see
#6473).

![r71](https://github.com/mrdoob/three.js/blob/master/src/core/BufferAttribute.js#L18-L22)

![r72dev](https://github.com/mrdoob/three.js/blob/dev/src/core/BufferAttribute.js#L18-L31)

Backward compatibility with r71 should be kept, otherwise, the method
should just be removed!

Implementation should be

```
get length () {

console.warn( 'THREE.BufferAttribute: .length has been deprecated.
Please use .count.' );
return this.array.length;

}
```

eg. / e.g.
vertice / vertex
fullframe / full-frame
todo / TODO
unreckognized / unrecognized
ontop / in front
initialise / initialize
unforms / uniforms
overriden / overridden
interpolatation / interpolation
subsurve / sub-curve
Catmull-rom / Catmull-Rom
consruct / construct
colinear / collinear
perpenicular / perpendicular
minimim / minimum
segements / segments
speficied / specified
compatable / compatible
egde / edge
initalization / initialization
shiftet / shifted
childrens' / children's
ambigious / ambiguous
barycoordinates / barycentric coordinates
equi distance / equidistant
equidistance / equidistant
ist / is

And remove one `console.log`

Doesn't seem like we need a console log every time PlaneGeometry is used. Is PlaneGeometry really that bad?

Minor weak for non-manifold scenario.

Anytime an edge is non-manifold (more than two faces sharing an edge, e.g. a 'T'), always keep the edge in the EdgesGeometry.

With the previous commit, when a third co-planar face was found, the edge was marked co-planar. I'm not sure which is right but this algorithm is a bit simpler.