local_extrema instead of coding sense of rotation with the sign of
extr_map.

In makefile, we want tags to include sources for test_good_contour,
etc. External file list becomes easier.

Moved test_bilinear_interp.f and test_bilinear_interp.py out of the
project. These are rather tests on Numer_Rec_95.

In test_local_extrema, write to CSV file instead of stdout.