Run over each file and run the import.  We could probably do this as a try/except and not delete if the output of the import failed but it may be simply easier to refetch those files from the S3 backup and try again.

options, quoting variables and a few other fixups.

default option if nothing is provided, and not bother passing true
when calling the subcommands.

repair the for filename part of sftp.

export commands handle --dest-from-settings and --destination and fail
unless one is provided as well as rename pearson.py to pearson_transfer
and allow is to call the import/export commands directly.

I've set it to die in pearson_transfer.py if the django PEARSON settings
aren't available.  I don't want to try and provide defaults, these must
exist or it simply fails.

clean.