Bug in optimised kernel generation for limiting ader-dg solver

Include file is wrong. Is _ADERDG.h for Limiting-ADER-DG solver.

/ddn/home/jdmd33/dev/ExaHyPE-Engine/./Benchmarks/hamilton/Euler/kernels/EulerSolver/stableTimeStepSize.cpp(7): catastrophic error: cannot open source file "EulerSolver.h"
  #include "EulerSolver.h"
                          ^