Improvements for GPU code generation

- turned on restrict keyword by default (makes large difference on GPUs)
- smarter block indexing: changing block size depending on domain size
  Example: previously there where (1,1,1) blocks when requested
  block size was (64, 1, 1) and domain size (1, 512, 512), now the
  block size is changed automatically to (1, 64, 1) in this case
- added __lauch_bounds__ to kernels to allow better optimizations from
  the CUDA compiler

lbmpy_walberla/templates/LatticeModel.tmpl.cpp

@@ -39,18 +39,13 @@
 #define FUNC_PREFIX __global__
 {%- endif %}
 
-#ifdef WALBERLA_CXX_COMPILER_IS_GNU
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wunused-variable"
-#pragma GCC diagnostic ignored "-Wunused-parameter"
-#pragma GCC diagnostic ignored "-Wshadow"
-#endif
-
-#ifdef WALBERLA_CXX_COMPILER_IS_CLANG
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wunused-variable"
-#pragma clang diagnostic ignored "-Wunused-parameter"
-#pragma clang diagnostic ignored "-Wshadow"
+#if ( defined WALBERLA_CXX_COMPILER_IS_GNU ) || ( defined WALBERLA_CXX_COMPILER_IS_CLANG )
+#   pragma GCC diagnostic push
+#   pragma GCC diagnostic ignored "-Wfloat-equal"
+#   pragma GCC diagnostic ignored "-Wshadow"
+#   pragma GCC diagnostic ignored "-Wconversion"
+#   pragma GCC diagnostic ignored "-Wunused-variable"
+#   pragma GCC diagnostic ignored "-Wunused-parameter"
 #endif
 
 
@@ -128,10 +123,6 @@ mpi::RecvBuffer & operator>> (mpi::RecvBuffer & buf, ::walberla::{{namespace}}::
 } // namespace mpi
 } // namespace walberla
 
-#ifdef WALBERLA_CXX_COMPILER_IS_GNU
-#pragma GCC diagnostic pop
-#endif
-
+#if ( defined WALBERLA_CXX_COMPILER_IS_GNU ) || ( defined WALBERLA_CXX_COMPILER_IS_CLANG )
+#   pragma GCC diagnostic pop
+#endif
\ No newline at end of file
-#ifdef WALBERLA_CXX_COMPILER_IS_CLANG
-#pragma clang diagnostic pop
-#endif