Refresh Rule-Based Auth ref-guide page

The Rule-Based Authorization page in the ref-guide could use some attention.

• the layout could be more logical (currently permission syntax is covered as a digression under the Authorization API, etc.)
• some relevant topics are missing altogether (permission-resolution ordering)
• the permission syntax is missing a lot of description in terms of default values, special keys, etc.

If this comes together quick enough, it'd be nice if we could get something better in front of users for 8.3