deletet all gpu related files, changed alle .cu files to .cpp files and add...

deletet all gpu related files, changed alle .cu files to .cpp files and add the licence text where it was still missing

src/gpu/GridGenerator/geometries/Sphere/Sphere.cpp

@@ -34,6 +34,7 @@
 
 #include <algorithm>    // std::min
 #include <float.h>
+#include <cmath>
 
 #include "geometries/Vertex/Vertex.h"