Create extension/package/namespace to capture information needed for parallel execution

[jonrkarr]

Several discussions have highlighted the need to execute SED-ML tasks in parallel -- see #54. This has led to clarifying the meaning of subtask/@order -- see #95.

To facilitate parallel execution, SED-ML needs more information. To avoid complicating the core of SED-ML, this could be placed in a separate namespace similar to SBML packages.

Additional classes/attributes could be added for this information. This would enable parallel execution, for example by conversion into a CWL file and execution with a CWL engine such as Airflow or Toil or conversion to Nextflow.

• Tasks
  • CPU requirements
  • Memory requirements
  • Walltime requirements
  • Preferred tool to execute the task (e.g., a URL for a Docker image)
  • Environment variables (e.g., for licenses to software)
• Subtasks
  • Dependency on other subtasks
• Outputs
  • Plot (creation) in particular needs similar information to tasks