SSO::PermissionSet InlinePolicy should be a json-string

[mello7tre]

Hi, as for subject, looking at AWS specification:
http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-sso-permissionset.html

SSO::PermissionSet InlinePolicy should be a json formatted string.
Currently is defined as a dict and in the final template output (yaml) is formatted "like" a yaml "object".

Best solution should be to allow parsing it as dict but to dump it in final template output using json.dumps (dunno if this is possible...)

Regards, Alberto.