Separate _put arguments for query and JSON-encoded body data in test client; test case showing pydantic model is required for list args

This reverts merge request !16

API test cases now call PUT through an internal method with re-attempts built in; trying to eliminate lost connections during testing but some still happen

Adapted base segmentation worklow and API endpoint for generic semantic segmentation model; made dummy model this type too

Validated non-duplication when loading ilastik model with same project file name, irrespective of path formatting

Repair automatic session restart, which was causing test client problems; corrected return value of model query