adjusted translation messages

as discusses here: https://github.com/tux3/qTox/pull/848#discussion_r20851990

src/widget/form/chatform.cpp

@@ -251,7 +251,7 @@ void ChatForm::onAvInvite(int FriendId, int CallId, bool video)
         connect(callButton, SIGNAL(clicked()), this, SLOT(onAnswerCallTriggered()));
     }
     
-    addSystemInfoMessage(tr("%1 calling").arg(f->getDisplayedName()), "white", QDateTime::currentDateTime());    
+    addSystemInfoMessage(tr("%1 is calling").arg(f->getDisplayedName()), "white", QDateTime::currentDateTime());
 
     Widget* w = Widget::getInstance();
     if (!w->isFriendWidgetCurActiveWidget(f)|| w->isMinimized() || !w->isActiveWindow())

translations/de.ts

@@ -234,7 +234,7 @@ Soll der Proxy ignoriert und eine direkte Internetverbindung genutzt werden?</tr
     </message>
     <message>
         <location filename="../src/widget/form/chatform.cpp" line="254"/>
-        <source>%1 calling</source>
+        <source>%1 is calling</source>
         <translation>%1 ruft an</translation>
     </message>
     <message>