fiber generator: real image and fiber extractor based workflow integration

[yuminguw]

• Match Real Data workflow: Complete the dedicated workflow for comparing synthetic outputs against real extracted data and using those comparisons to guide or tune generation.
• Extractor / extracted-data workflow integration: Finish integrating an extracted-data workflow so external centerlines, masks, or measurements can be brought into the same internal pipeline.
• Image input workflow: Complete the workflow where a real input image can be used as a template or reference for generating a similar synthetic network.

Use CT-FIRE as the default fiber extractor .