get phantomkit to work on XNAT

[arkiev]

DEPENDENCIES

• convert python scripts to pydra
• build on XNAT
• test XNAT functionality

[arkiev]

• decided to keep file identifier component that is part of orchestration script within phantomkit, and create a separate pipelines-wide file identifier workflow that reads not just filenames

[arkiev]

Had a go at pydrafying phantom_processor.py (seems to work, will do more testing over the next few nights).

Single_workflow branch contains the most recent version of scripts