* Examples: use .texture of input render targets.

* Assign null instead of undefined.

remove material.ambient from everything per discussion here: https://github.com/mrdoob/three.js/pull/5741#issuecomment-67893202

Also change use of setClearColorHex to setClearColor.

Cleaned up custom stats.js styling in examples (thanks to @mrdoob for showing me this is possible ;).

Renamed screen shader to blit.
Throwing errors in *Pass if the shader aren't available.

All examples should work now.

The only weird thing seems to be that for some reason bone texture doesn't like to be assigned to arbitrary texture unit (or more precisely to alternating texture units).

See #2340

Sorry that you had to add it @alteredq.

Still needs to be done: canvas renderer / picking / canvas examples.