add sip registrars menu item
registrar dialog mockup
sketch registrars dialog
controller: report any weird dialog return
wip: RegistrarsModel
RegistrarDlg as gobject-style parameters
wip: RegistrarModel and RegistrarDlg
controller: code style fix
dialog: the model is a class attribute
wip: RegistrarModel and RegistrarDlg
dialogs: spinner timeout function