Improved COLLADA Resource Loading

Bug Fixes

• instantiate_model: fix issue where whole model wasn't instantiated (591db7b0)
• parse-collada: correctly interpret xs:anyURI type (a1385042, breaks #)
• polygon::Mesh: derive Clone impl for Mesh (7fc1d2e8)
• transform: fix bug where child hierarchies aren't re-parented (ee702628, closes #47)

Breaking Changes

• parse-collada: correctly interpret xs:anyURI type (a1385042, breaks #)

Improved Mesh Compilation

Breaking Changes

• parse-collada: rename PrimitiveType to PrimitiveElements (f1cd6b4a, breaks #)
• polygon::MeshBuilder: remove Mesh::from_raw_data() and replace it's functionality with MeshBuilder. (907bf23c)

Features

• parse-collada:
  • add implementation for primitive elements (953ac4bd)
  • better support parsing normal data (6edf9162)
• polygon-math::Vector2:
  • add Vector2::as_ref() (d7eda56c)
  • add Vector2 type and other utilities (137f3c36)
• polygon::MeshBuilder:
  • support texcoord vertex attributes (03e875c7)
  • add mesh builder system (907bf23c)
• resource::collada:
  • process texcoord vertex data (a87e2c96)
  • more robust collada mesh processing (bb075efa)

Bug Fixes

• parse-collada: rename PrimitiveType to PrimitiveElements (f1cd6b4a, breaks #)