Add a toggle for showing traffic in notification.

TODO: Disabling it causes weird behavior. :-(

src/main/res/values/strings.xml

@@ -13,6 +13,7 @@
   <string name="nat_summary">Use NAT mode instead of VPN mode</string>
   <string name="nat_summary_no_root">NAT mode is disabled without root</string>
   <string name="stat">Network Traffic</string>
+  <string name="notification_traffic">Show traffic in notification</string>
   <string name="stat_summary">Sent: \t\t\t\t\t%3$s\t↑\t%1$s/s\nReceived: \t%4$s\t↓\t%2$s/s</string>
   <string name="stat_profiles">\n%1$s↑\t%2$s↓</string>
   <string name="traffic_summary">%1$s/s↑\t%2$s/s↓</string>
@@ -55,8 +56,6 @@
   <string name="bypass_apps_summary">Enable this option to bypass selected apps</string>
   <string name="auto_connect">Auto Connect</string>
   <string name="auto_connect_summary">Enable Shadowsocks on startup</string>
-  <string name="traffic_stat">Traffic Stats</string>
-  <string name="traffic_stat_summary">Show traffic stats in notification bar</string>
   <string name="udp_dns">UDP Forwarding</string>
   <string name="udp_dns_summary">Forward UDP packets to remote</string>