Vizard: add nodes.

There are some nodes we'd better remember.

<viz>.addRenderNode
<viz>.addRenderTexture
<viz>.addBlankTexture
<viz>.addTexture
<viz>.addTextureFromBuffer
<viz>.addVideo
<viz>.addAudio

<viz>.addGroup
<viz>.objectGroup


Display background texture
http://kb.worldviz.com/articles/813