detect_onsets with and without presets

[ivanlmh]

In the examples folder, detect_onsets.py and detect_onsets_presets.py are coexisting. They are different and they may be complementary, are we going to keep both?

[ivanlmh]

From our 3rd of March meeting:
It actually doesn't make much sense to have a script with so many hardcoded parameters, people have to go in and edit to use it.
It ends up being halfway between a useful script and an example.
Maybe we should have a "scripts" folder separate from the "examples" one.