[test] minor changes in test_2U_2_nondiag. Ongoing work
[src] fixed again setReferenceBandwidth
[src] minor optimization with the distribution class
[src] minor cosmetics in computePDFOn1DGrid : use of computeEquivalentPDFSum and optimization of some computations using reindexation
[test] updated test_2_1 : use of computePDF both on a grid and on some points
[test] added trace of test_2_1
[test] minor changes of test_2U_1T
[test] update of test_2U_1T trace
[test] update of graph results due to recent changes