sequential version working, also only approx 1.5 eoc in l2,

block_structures/block_matrix_t.cpp

block_structures/block_matrix_t.hpp

block_structures/block_vector_t.cpp

block_structures/block_vector_t.hpp

gaulhofer/heat_solver_simple.cpp

gaulhofer/heat_solver_simple.hpp

gaulhofer/int_test_heat_simple.cpp