Reading/writing markup

[tracend]

The library needs to be able to read and write markup.

As it is currently structured the createCamera() and addCamera() are complementary methods but don't seem to cover all the different cases.

Specifically, we can read existing markup but adding new elements won't create the necessary markup (as calling createCamera after addCamera will insert the logic in an infinite loop).

Obviously we need a third method that handles exclusively the generation of the WebGL content...

[tracend]

The new method(s) will take up the namespace "webgl" and the relevant code will be placed in its own (new) file, suitable named three.js