title: Remove existing annotation and add new annotation into the mapview
body: <p>I am loading a mapview with a single annotation. Just like the "map app" in iphone. I have a search bar, which shows the address of the pin location, shown in map. Now I decide to change the location address. I type a new address location in the search bar. Then my mapview has to remove the existing annotation and add the new annotation. Right now, I am adding the new annotation, but I am unable to remove the existing annotation. How can I remove that  existing annotation?</p>