Add some fixes to update UV-Net to run on the s2 release of the Fusion Gallery segmentation dataset

[JoeLambourne]

Fusion Gallery Segmentation Dataset Compatibility

The second release of the Fusion Gallery Segmentation Dataset uses STEP data in place of Autodesk SMT files. The extended STEP dataset provides an additional 7054 models which were too complicated to mesh for MeshCNN.

The s2.0.0 release places the STEP and segmentation information in the following folder structure

s2.0.0
  |
  +-- breps
          |
         +-- step    (STEP data in here) 
          |
         +-- seg    (segmentation labels in here)

Also to get this working we need to

• Convert float64 to float32 values
• Filter out models with no edges

It is also valuable to allow the number of input curve features to be adjusted.

Monitor accuracy as well as IoU

There is no way to monitor segmentation accuracy. This is now added to the segmentation model.