Each morning, Amy Parker and her husband Michael Palmer step from their front porch into a sanctuary nestled among flowers and rocks shaded by trees, luring butterflies and bees to stop and pollinate.   The Sacramentans recently transformed the front yard of their 10-year-old home into an inviting rock garden. Before it became a garden, the space was a lawn with fruit trees. Now it is abundant with colorful plants that require short watering sessions throughout the week.   Currently, city code allows Sacramento residents to water their yards three times per week during the summer. The Sacramento City Council passed additional changes to the outdoor water conservation ordinance, which t