Allow scalars for resources and actions in JSON

[aajtodd]

The current policy JSON looks like:

        {
            "name": "Account policy",
            "statements": [
                {
                    "sid": "Grant all read access on specific account",
                    "effect": "allow",
                    "actions": ["account:describe:*"],
                    "resources": ["resource:account:789"]
                }
            ]
        }

We should allow either actions or resources to be scalar strings for convenience.

        {
            "name": "Account policy",
            "statements": [
                {
                    "sid": "Grant all read access on specific account",
                    "effect": "allow",
                    "actions": "account:describe:*",
                    "resources": "resource:account:789"
                }
            ]
        }

[aajtodd]

closed by 5dea014