timestamp has been added to grp sync item
updated data service and grps to deal with this
added msg and grp meta types which serves to hold meta data of grp and msg
removed observer temporarily
updated nxs item tests, need to update data service tests
git-svn-id: http://svn.code.sf.net/p/retroshare/code/branches/v0.5-new_cache_system@5256 b45a01b8-16f6-495d-af2f-9b41ad6348cc
