Add a menu item to hide/show the search bar

po/fr.po

po/sflphone.pot

sflphone-gtk/src/configurationmanager-glue.h

sflphone-gtk/src/dbus.c

sflphone-gtk/src/dbus.h

sflphone-gtk/src/historyfilter.c

sflphone-gtk/src/mainwindow.c

sflphone-gtk/src/menus.c

sflphone-gtk/src/sflphone_const.h

src/dbus/configurationmanager-glue.h

src/dbus/configurationmanager-introspec.xml

src/dbus/configurationmanager.cpp

src/dbus/configurationmanager.h

src/managerimpl.cpp

src/managerimpl.h

src/user_cfg.h