Customization to make it easier to deal with bootstrapping data from iam create-virtual-mfa-device

This customization makes it easier to deal with the bootstrapping data returned by the ``iam create-virtual-mfa-device`` command.  You can choose to bootstrap via a QRCode or via a Base32String.  You specify your choice via the ``--bootstrap-method`` option which should be either "QRCodePNG" or "Base32StringSeed".  You then specify the path to where you would like your bootstrapping data saved using the ``--outfile`` option.  The command will pull the appropriate data field out of the response and write it to the specified file.  It will also remove the two bootstrap data fields from the response.