Add identication option to user_groups record

[WanWizard]

Currently, when a module_installer creates user_groups for the module, there is no way the module code can reliably access the created group. Currently, this is done on group_name, but as this can be changed by the administrator, a more reliable method needs to be found.

Suggestion: use the assigned module_admin_rights code, as this is unique per (official) module, followed by a 2 digit sequence number, p.e. AA01, AA02...

This can be used by the module itself to find the correct user_group record (p.e. to add users to the group), or to remove the group when the administrator deinstalls the module.

[WanWizard]

Added in changesets [850] through [858].

Also changed the code for the user_groups admin panel, so groups with an associated group_ident can not be deleted (because the module_installer is responsible for that when you uninstall a module).

Modified the advertising admin panel, so that when a new sponsor is added, his/her user_id will be added to the Sponsors user_group (identified by group_ident 'wE01')