Final preparation of OS2.5.1 specification
Merge pull request #1332 from OpenSocial/master

Issue-1333/GH-1302: Update spec language to use SHOULD key word
Remove draft tags from OpenSocial 2.5.1 specs
Merge pull request #1333 from OpenSocial/251_staging

Merge 251 staging into trunk (remove draft tags, prepare final draft)