GUI-337: Initial Progress on IAM Policy Wizard

Opening this pull request now since we have a working IAM Policy Wizard in place, and we can start hooking it up to "Add Policy" actions from a given user or group.

@dkavanagh , @kyolee310: To link to the policy generator from a user page, use the following as the URL…

`${request.route_url('iam_policy_new')}?type=user&id=fred`

…and for groups use type=group

Note that the policy generator is missing key features, such as the "Advanced" options to specify resources and conditions for Allow/Deny statements.  Those will be developed next week.

Also note that the wizard displays a "live preview" of a policy generated via the policy generator.  The split-view has proven to be useful during development, but we can easily swap it out for the "3-step" wizard if necessary.  Need to discuss with @JMoLo next week.