CityGML 3.0 texture support

[mlavik1]

Hello, me again! Here's a PR with CityGML 3.0 texture support. Please let me know if you want me to change something in my PR (no hurry) Again, thanks a lot for making this library :)

NOTE: You may want to merge #91 first

CityGml 3.0 does not only introduce new features - it also changes some existing ones (see below).

Changes from CityGML 2.0:

• "app:surfaceData" is now "app:surfaceDataMember" (see commit in CityGML3.0Encodings repo)
• "app:target" no longer resides directly under "app:ParameterizedTexture".
  • New structure: "app:ParameterizedTexture" -> "app:textureParameterization" -> "app:TextureAssociation" -> "app:target". See schema
• Previously the "target" child element (a TextureAssociationType) of used to have a "uri" attribute. In CityGML3.0, "target" is an element of type anyURI (see schema)
• "app:ring" replaces the "ring" attribute of "app:textureCoordinates"

Due to all these changes, I decided to create a new TextureAssociationElementParser, for "app:TextureAssociation" elements.

Test datasets:

• Helsinki_v3.gml

[jklimke]

Hi @mlavik1. First of all thank you for your contribution. I will need a little time tolook into it and merge your changes.

[mlavik1]

Hi @mlavik1. First of all thank you for your contribution. I will need a little time tolook into it and merge your changes.

Ok, no hurry! We're using our own fork where these PRs are merged in, so take your time :)