* move is* properties to prototypes and remove unused ones

* rebuild

* merge dev -> less-is

* remove rebuild from PR

* convert to ES modules

* rebuild

* move shaders back into glsl files

* reinstate polyfills

- Better inheriting of `clone` + `copy` methods where appropriate. This is done by calling `new this.constructor()` in parent classes. `this.constructor` refers to the current instance's constructor, so it should all compose nicely;

- Pass in attributes directly as arguments to constructor when cloning, where appropriate (if arguments pattern is different from parent class). This mean `copy` isn't relied on to set those attributes.

- Change order of `clone` in some files (for better visibility into its relationship with `copy`, and to maintain consistency; can return to previous order if necessary);

- Fix CubeTexture's clone method

Removed setGeometry() and setMaterial() from Mesh. Moved the boundSphere check to Frustum and Raycasting.

Misteriously when using the latest version of the lib on the project I'm working on I'm getting this error:
> Uncaught TypeError: Object [object Object] has no method 'set'
This is caused when THREE.UniformsLib.common.diffuse initialises a THREE.Color (THREE.Color.set() seems to be undefined then).
For some reason this only happens when I load Box2D before three.js. If I load it after is all good. But this fixes the problem too.
/ping @bhouston

fix three missed conversions to closures.  switch to extending math prototypes rather than replacing them.  This is to ensure that types created in closures within a type's prototype definition get their prototype updated with the full definition.

update math constructors to not copy when provided explicit initial values per @mrdoob: https://github.com/mrdoob/three.js/pull/2902#issuecomment-11999928

Frustum bug fix: clone and constructor should be real copies.  Fix bug in unit test to catch this in the future.

Also, code clean up here and there.

Frustum.contains -> intersectsObject, containsSphere->intersectsSphere, removed Frustum.containsAnyPoints, .transform.  Update unit tests accordingly.