Extern Incoming call string.

Fixes #4196
// FREEBIE

src/org/thoughtcrime/redphone/ui/CallScreen.java

@@ -64,7 +64,7 @@ public class CallScreen extends FrameLayout {
   }
 
   public void setIncomingCall(Recipient personInfo) {
-    callCard.setCard(personInfo, "Incoming call");
+    callCard.setCard(personInfo, getContext().getString(R.string.CallScreen_Incoming_call));
     callControls.setIncomingCall();
   }