Swagger definition API: Add enum to the file API

Swagger definition API support enum to limit the allowed value.

When the enum is used the Swagger UI will translate the possible value
to a pull down list.

Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>
Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
Swagger Definition API: file permission should be octet string

Change the file permission type to be octet represtated as string

Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>
Signed-off-by: Avi Kivity <avi@cloudius-systems.com>