Can't access model companion directory from Runner/WorkflowJSON in Apply Measure Now

[macumber]

Apply measure now uses a temp model and sandbox to protect the working model. However, we need a way to access files in the model's companion directory. Use cases are:

• Write an html report to the reports directory
• Write a csv file to the model's data dir
• Read a file from the model's data dir

We need to make sure to revert all changes if the user cancels. Suggest that we initialize a temp model companion dir with all files, then merge that back on accept.

[macumber]

@jmarrec FYI

[jmarrec]

I think the issue title might be a bit misleading. The companion dir can be accessed (or should be accessible) via WorkflowJSON I think. The path to the original model dir cannot however.