Revert to using image prop and use @2x @3x images

mobile/src/Home/Home.js

@@ -14,6 +14,7 @@ import { api } from "../API"
 import autobind from "autobind-decorator"
 import { ifIphoneX } from "react-native-iphone-x-helper"
 import { workItemTypeText, pad } from "../util"
+import pinImage from "./images/pin.png"
 
 const styles = StyleSheet.create({
   container: {
@@ -137,9 +138,9 @@ export class Home extends React.Component {
               }
               description={workItem.address}
               anchor={{ x: 0.5, y: 1.0 }}
-              onPress={(e) => this.handleMarkerPress(e, index)}>
-              <Icon name="pin" size={24} />
-            </Marker>
+              image={pinImage}
+              onPress={(e) => this.handleMarkerPress(e, index)}
+            />
           ))}
         </MapView>
         <View