Add doc on 1.6.0 upgrade and its breaking changes
Add doc on 1.6.0 upgrade and its breaking changes

Extensions won't work if they aren't upgraded as well.
bearstech/modoboa,bearstech/modoboa,carragom/modoboa,tonioo/modoboa,tonioo/modoboa,modoboa/modoboa,modoboa/modoboa,carragom/modoboa,tonioo/modoboa,bearstech/modoboa,modoboa/modoboa,carragom/modoboa,modoboa/modoboa,bearstech/modoboa