Remove lapack linking

This PR implements an alternate strategy to bind BLAS/LAPACK routines based on importing functions at run time via C-pointers provided by scipy. I removed any attempt to link BLAS/Lapack libraries at build time, even using source code (the lapack-lite distribution therefore becomes obsolete).

Because not all the BLAS/LAPACK functions are available through scipy, I had to slightly rewrite some parts of the fff library and the `labs` package. The tests are however unchanged and all pass on my box.