qt5: full qt5 compability

ifdef rest of the code which can't be ported 100%
add CMake option USE_QT5 to use qt5 ;)
Thanks to stretchtiberius for initial patch

src/FilterTableHeader.cpp

@@ -8,7 +8,11 @@ FilterTableHeader::FilterTableHeader(QTableView* parent) :
     QHeaderView(Qt::Horizontal, parent)
 {
     // Activate the click signals to allow sorting
+#if QT_VERSION >= 0x050000
+    setSectionsClickable(true);
+#else
     setClickable(true);
+#endif
 
     // Do some connects: Basically just resize and reposition the input widgets whenever anything changes
     connect(this, SIGNAL(sectionResized(int,int,int)), this, SLOT(adjustPositions()));