unexpected behaviour in SecondOrderPartialTestPartialTrial.hpp
Instead of partial_i partial_j the operator seems the to return partial_j partial_j.
Found problem in Lines 57 and 58: rowPartial and colPartial share same memory adress
Example u(x)=x^2 on a Grid (-2,2) times (-2,2) with d_y d_x u =0, d_y u = 0 on the upper and lower boundary, u(.,y)=4 on the left and right boundary