exchange: Implement refresh_account
exchange: Implement refresh_account

Fixes: https://bugzilla.gnome.org/667889

ritzk/gnome-online-accounts,Distrotech/gnome-online-accounts,halfline/gnome-online-accounts,dnohales/gnome-online-accounts,felipeborges/gnome-online-accounts,Distrotech/gnome-online-accounts,halfline/gnome-online-accounts,halfline/gnome-online-accounts,dnohales/gnome-online-accounts,ritzk/gnome-online-accounts,felipeborges/gnome-online-accounts,ritzk/gnome-online-accounts,felipeborges/gnome-online-accounts,dnohales/gnome-online-accounts,Distrotech/gnome-online-accounts