[#3621] Display multiple chat windows in tabs

sflphone-client-gnome/src/callable_obj.c

sflphone-client-gnome/src/callable_obj.h

sflphone-client-gnome/src/dbus/dbus.c

sflphone-client-gnome/src/imwindow.c

sflphone-client-gnome/src/imwindow.h

sflphone-client-gnome/src/uimanager.c

sflphone-client-gnome/src/widget/imwidget.c

sflphone-client-gnome/src/widget/imwidget.h

sflphone-client-gnome/webkit/Makefile.am

sflphone-client-gnome/webkit/im/chat_info.png

sflphone-client-gnome/webkit/im/im.css

sflphone-client-gnome/webkit/im/im.html

sflphone-client-gnome/webkit/im/im.js