SCRIPTS: Various minor fixes in interpolation sandbox script

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
SCRIPTS: Added an utility method for zero crossing computation

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
FILTERS: Moved Pi definition into a common file

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
TESTS: Added a simple sinus generator for testing purpose

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
SCRIPTS: Added a Sinus generator for testing purpose

This one is the Python script version.

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