Add RELEASENOTES for 1.2.3
Add RELEASENOTES for 1.2.3

Change-Id: I571c3dcd56619b3f5c337181ba16583f474c214f

openstack/openstackdocstheme,openstack/openstackdocstheme,openstack/openstackdocstheme,openstack/openstackdocstheme,vauxoo-tests/vauxoodocstheme,vauxoo-tests/vauxoodocstheme,vauxoo-tests/vauxoodocstheme