Drafting this here.

Currently XMB is using some sort of powerlevel system with constants defining the groups hardcoded when it needs to.

This is pretty basic, but if we want to go further, and perhaps alter an individual permission, or have a group that inherits other permissions, we cannot do this!

So maybe we need to have a new system, something that works a little more flexibly.

xmb_groups structure:
- gid - The group ID
- name - The group name
- member_title - The member title shown by default
- htmlclass - The HTML class used for styling the userlink
- l10n - Used for localisation text strings
- subgroupof - If 0/NULL/empty/whatever, it is not a subgroup
- permissions - I don't know how this is going to work tbh
- order1 - Affects the displayed order in the front end
- order2 - Affects the order of permission inheritance
- massu2u - Can be mass-U2U'd by other users
- special - Any 'special traits' of this group, whatever those could be

I haven't really thought out anything else about this, except that this is probably the basic stuff that would be needed in part of the SQL table...