Add XML3D output format to W3DS community module

This pull request adds XML3D support to W3DS community module.

Main features are ability to create XML3D objects from elevation information, support for external referenced XML3D objects and octet-stream output, which returns only elevation information in binary format.

Here is also a screenshot from our demo client:
![gis_client](https://f.cloud.github.com/assets/582411/2304231/5f156a04-a20e-11e3-9159-14ae5d78f9c8.jpg)