DESCRIPTORS: Remove dependencies to the manager in the Process() method

The Process() method is supposed to be independent from the manager.
This is now the case.
Part of #39.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
TESTS: KissFFT usage now cleaner - direct access to the Process() method

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
DESCRIPTORS: Move internal common parameters into the manager

These are the bin indexes parameters delimiting the Dft bins
to be considered.
Part of #37.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
ALGORITHMS: Remove useless parameter from the scale generator

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
DESCRIPTORS: Move frequency scale generator into the manager

Fixes #37.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>