[FIX] mail: mail_message write right
[FIX] mail: mail_message write right

Notified people should be able to write on the message, for example to be
able to star / unstar, needactionize / unneedactionize (nice word).

hip-odoo/odoo,ygol/odoo,syci/OCB,syci/OCB,bplancher/odoo,ygol/odoo,optima-ict/odoo,ygol/odoo,bplancher/odoo,sysadminmatmoz/OCB,bplancher/odoo,Elico-Corp/odoo_OCB,hip-odoo/odoo,sysadminmatmoz/OCB,microcom/odoo,storm-computers/odoo,stephen144/odoo,stephen144/odoo,sysadminmatmoz/OCB,dfang/odoo,optima-ict/odoo,hip-odoo/odoo,dfang/odoo,microcom/odoo,microcom/odoo,stephen144/odoo,storm-computers/odoo,storm-computers/odoo,optima-ict/odoo,syci/OCB,laslabs/odoo,Elico-Corp/odoo_OCB,laslabs/odoo,syci/OCB,laslabs/odoo,ygol/odoo,sysadminmatmoz/OCB,syci/OCB,microcom/odoo,storm-computers/odoo,optima-ict/odoo,microcom/odoo,hip-odoo/odoo,laslabs/odoo,ygol/odoo,laslabs/odoo,stephen144/odoo,dfang/odoo,optima-ict/odoo,laslabs/odoo,Elico-Corp/odoo_OCB,syci/OCB,storm-computers/odoo,Elico-Corp/odoo_OCB,storm-computers/odoo,dfang/odoo,stephen144/odoo,Elico-Corp/odoo_OCB,hip-odoo/odoo,sysadminmatmoz/OCB,microcom/odoo,hip-odoo/odoo,bplancher/odoo,dfang/odoo,sysadminmatmoz/OCB,stephen144/odoo,sysadminmatmoz/OCB,ygol/odoo,bplancher/odoo,optima-ict/odoo,bplancher/odoo,ygol/odoo,dfang/odoo,Elico-Corp/odoo_OCB