Update vim-create and vim-update to accept config and credential files

vim-create will accept both a config dict and a config file, with respective
options "--config" and "--config_file". If a key is present in both, the
value in the config dict will prevail.

In addition, vim-create command will accept a new option --creds, required
for Google Cloud Platform (GCP) due to the way the authentication works in
GCP. That option is codified directly in the config dict that is sent to the
NBI, under config["credentials"]. The RO connector for GCP will receive it
and will expect those credentials in that dictionary. In the future, other
RO connectors might use a similar approach.

Finally, this change also adds the option --literal to vim-show command.

Change-Id: Ifb4c284593b171353b6c180bdc7af75e8a25dfac
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>