[x3d-public] add description fields to all texture nodes

[Don Brutzman]

While working on Shape and Texture components today, Dick noticed that we were inconsistent about adding 'description' field to various texture nodes.

Seems like a good idea for both 2D and 3D texture nodes.

* Mantis 1326: add description field to all textures
   Description	For consistent interaction support, include description field for all texture nodes.
   https://www.web3d.org/member-only/mantis/view.php?id=1326

Appropriate description of description (cough cough):

"The description field provides textual information about the image data."

Affected nodes and interfaces:

- X3DTextureNode, X3DSingleTextureNode, X3DTexture2DNode, MultiTexture, PixelTexture
- X3DTexture3DNode,ComposedTexture3D,  PixelTexture3D
- X3DEnvironmentTextureNode, ComposedCubeMapTexture, GeneratedCubeMapTexture

Applied to spec and checked in, changes to X3D Schema DTD and X3DUOM to follow.

all the best, Don
-- 
Don Brutzman  Naval Postgraduate School, Code USW/Br       brutzman at nps.edu
Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA   +1.831.656.2149
X3D graphics, virtual worlds, navy robotics http://faculty.nps.edu/brutzman