New call button not enabled when no accounts

sflphone-gtk/src/accountlist.c

sflphone-gtk/src/accountlist.h

sflphone-gtk/src/accountwindow.c

sflphone-gtk/src/accountwindow.h

sflphone-gtk/src/actions.c

sflphone-gtk/src/actions.h

sflphone-gtk/src/calllist.c

sflphone-gtk/src/calllist.h

sflphone-gtk/src/calltree.c

sflphone-gtk/src/calltree.h

sflphone-gtk/src/configwindow.c

sflphone-gtk/src/configwindow.h

sflphone-gtk/src/dbus.c

sflphone-gtk/src/dbus.h

sflphone-gtk/src/dialpad.c

sflphone-gtk/src/dialpad.h

sflphone-gtk/src/main.c

sflphone-gtk/src/mainwindow.c

sflphone-gtk/src/mainwindow.h

sflphone-gtk/src/menus.c