Improve stored password management
Landing the new accounts editor has made the "save_password" account pref hidden - there's no UI for it any more. Also, there's no way to clear saved passwords either, aside from opening Seahorse or deleting the account. Deleting passwords from Seahorse sucks at the moment though because the label doesn't contain the login or server name, just "Geary IMAP password", etc, in English.
I feel like all of the above is probably fine, as long we fix the label used for the secret to be translated and include more info to make it easier to find in when searching for it in Seahorse.
For save_passwords however, if its going to remain a hidden account pref, then the tickbox on the password dialog should go away.