tiny typo
rewrite of 4.1.2 Actor

plus some changes to identified group property table
forgot change two words
and a typo...
Merge branch 'master' of https://github.com/adlnet/xAPI-Spec
Updated rewrite of 4.1.2 Actor

based on Andrew's and Russel's review comments. Thanks.
Merge pull request #86 from paul-esch/master

Rewrite of 4.1.2 Actor