This adds the "batch_upload_tasks" argument to "arc tasks" which
accepts a path to a CSV file. The CSV file is read, and is used
to create multiple tasks at one go.
The first column of the CSV file should be the alias, and the second
column the summary. It is assumed that this workflow will require
the users to triage and add more detail once they are working on a task.
The CSV should be comma separated, and delimited by "", which is the default
behaviour of PHP's CSV parser.