Change Group section to agentGroup, move agentClass to proposals/

[dmitrizagidulin]

Updating the WAC spec (the Group section) to reflect design meetings with @timbl.

[timbl]

"Since Group Listings (which are linked to from ACL resources using
-the acl:agentClass predicate) are regular documents, they can have their very +the acl:agentGroup predicate) are regular documents, they can have their very"

Correction. The group in general won't be a document but will be a LD thing mentioned in a document which lists its members, like Friends.ttl#this
Looking it up -- dereferencing it -- will load Friends.ttl which will give a series triples of the from

Friends.ttl#this vcard:hasMember ?m

[timbl]

Some systems may 'pun' using the same name for a group and a docuemnt but this is not recommended

[dmitrizagidulin]

@timbl - Updated the phrasing to take your correction into account.