File deletion v2

[jabrah]

Could use an eye on error handling.

Error handling in general is a bit of a mess in pass-ui, but specifically for file deletion, we want to try to handle error cases where the File entity could get into a weird state:

• Deletion of the file bytes has to be handled separately from removal of the File (metadata) entity in the database
• File entity has a URI reference to the bytes, pointing to where the file service can operate on the file
• Getting these two out of sync could be problematic in the Files step, submission review page, or submission details page

Changes

• Provide custom File model adapter:
  • Call to FIle.destroyRecord will delete file bytes via the File Service before calling standard destroyRecord in the Ember store
• Update/add tests for workflow-files component