Merge branch 'compare_at_gauss_points' into devel

include/libgmshdg/gmsh_io.h

include/libgmshdg/param_loader.h

include/maxwell/maxwell_postpro.h

share/examples/capacitor/capacitor.geo

share/examples/capacitor2/capacitor.geo

share/examples/capacitor2/params_capacitor.lua

share/validation/params_resonator_gmshfem_comparison.lua

share/validation/resonator.geo

src/libgmshdg/gmsh_io.cpp

src/libgmshdg/param_loader.cpp

src/libgmshdg/physical_element.cpp

src/maxwell/maxwell_postpro.cpp

src/maxwell/maxwell_solver.cpp

tests/test_basics.cpp

tests/test_differentiation.cpp

tests/test_differentiation_gpu.cpp

tests/test_lifting.cpp

tests/test_lifting_gpu.cpp

tests/test_mass.cpp