Vector operators

This MR extends the HOG to enable the generation of vector-vector operators using the tensorial vector function spaces.

Those are relevant for two reasons:

• communication patterns should improve compared to "block-scalar" operators
• enables the implementation of certain forms that are not possible or at least complicated with scalar operators (e.g., Nitsche + free-slip BCs)

Still WIP until the following points are resolved:

• P1 support (first 2D results are looking good)
• P2 support
• 3D
• automated testing
• viscous ops with blending should be tested to make sure the full feature set is covered
• cleanup (check duplicated code in hyteg-coupling, forms, ...)

hyteg_integration_tests/src/EpsilonVector.cpp

@@ -21,7 +21,7 @@
 #include "core/DataTypes.h"
 
 #include "hyteg/elementwiseoperators/P2ElementwiseOperator.hpp"
-#include "hyteg/src/constant_stencil_operator/P2ConstantEpsilonOperator.hpp"
+#include "constant_stencil_operator/P2ConstantEpsilonOperator.hpp"
 #include "hyteg/forms/form_hyteg_generated/p2/p2_epsilonvar_affine_q4.hpp"
 #include "hyteg/p2functionspace/P2Function.hpp"