Fix bandpass Butterworth filter order to get a better filter, add option to change order in CLI

[smoia]

Addresses and possibly fixes #89
@farnazdelavari if you can test again the new version of the code vs your matlab impementation, I'd appreciate it.

Proposed Changes

• Changes default Butterworth filter order from 1 to 9 to get a steeper change
• Add option to change order in filter function, workflow, and CLI

Not super-happy about how the power spectra post-filtering looks like, a bit more work might be needed here!

Change Type

• bugfix (+0.0.1)
• minor (+0.1.0)
• major (+1.0.0)
• refactoring (no version update)
• test (no version update)
• infrastructure (no version update)
• documentation (no version update)
• other

Checklist before review

• I added everything I wanted to add to this PR.
• [Code or tests only] I wrote/updated the necessary docstrings.
• [Code or tests only] I ran and passed tests locally.
• [Documentation only] I built the docs locally.
• My contribution is harmonious with the rest of the code: I'm not introducing repetitions.
• My code respects the adopted style, especially linting conventions.
• The title of this PR is explanatory on its own, enough to be understood as part of a changelog.
• I added or indicated the right labels.

• I added information regarding the timeline of completion for this PR.

• Please, comment on my PR while it's a draft and give me feedback on the development!

[smoia]

🚀 PR was released in 0.18.1 🚀