Update server code integration for QtWebApp 1.7.11

- Adapt server code for QtWebapp namespace 'stefanfrings'
- Implement custom modifications needed by v1 controller
  via template engine
- Unify iphone and ipad templates

YACReaderLibrary/server/controllers/v2/foldercontentcontroller_v2.cpp

@@ -14,6 +14,9 @@
 
 #include <chrono>
 #include <ctime>
+
+using stefanfrings::HttpRequest;
+using stefanfrings::HttpResponse;
 using namespace std;
 
 struct LibraryItemSorter {