Allow more granular permissions for the Confluence Administrator role

Issue Summary

It would be useful to have a more granular way to control Confluence Administrator permissions. At present, granting Confluence Administrator permissions gives the user access to modify all settings associated with Confluence for the entire site. An example of how this could be helpful, is where an app requires a  user to have the Confluence Administrator role to administer their app settings. Giving the user these elevated permissions to all of Confluence is excessive if they only need to manage the app. Another scenario is where you may want to grant a user the ability to manage the look and feel of Confluence, but not the other security and administration features.