Draft for inclusion of surface textures and materials

[situx]

This pull request proposes to include textures and materials by examining related work such as CityGML/CityJSON, among others.
Finishing this pull request will close #438

The following contents are defined:

• Classes and properties for Materials and Textures
• Connection of surfaces to textures and materials (This part depends on the definition of 3D geometries in GeoSPARQL, which will be a separate pull request)

TODO:

• Evaluating whether literals need to be defined to store textures in the knowledge graph
• Cross-checking with the pull request for geometry styles in 2D Draft to include styles for features #418