Categories Math, Scientific Computing, Chemistry and Biology

- Scientific Computing includes Chemistry and Biology.

- Some projects are in inappropriate categories.

For example, `fftw` in Scientific Computing should be in Math, because Fourier Transformation is a math problem and its application is not only in scientific computing. It would be more "Mathematical" than `QuantLib` in Math.

- What about graph computing frameworks and libraries, solving problems like broad-first search, single-sourcce shortest path, etc.? They are combinatorial math solver, but not like the numeric solvers in Math.