Add tools to support processing with AddBiomechanics

[nickbianco]

As the AddBiomechanics web processing application has become more popular, users are asking if we plan to support the processing pipeline in the OpenSim GUI. This will likely require changes in both this repo and the AddBiomechanics repo, but creating this issue here to start the planning conversation.

AddBiomechanics provides a command-line interface that for uploading data and downloading the results of processing jobs. We might be able to leverage the CLI in a tool (or set of tools) for manage data and jobs in the GUI.

Some things to consider:

• AddBiomechanics user authentication, so the GUI tool(s) will need to safely access and pass this information to the CLI
• The amount of time needed to process a job varies after uploading data. Therefore, it might make sense to have separate upload/download jobs.
• We will probably need to locally store job IDs to manage uploads and downloads.
• Should we visualize currently processing jobs in GUI (ala the OpenCap web interface)?

[nickbianco]

@aymanhab, I've updated this issue per our discussion yesterday.