Remove unneeded parameters

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Overview

Remove unused parameters and parameters with file extensions. Moved all relevant system parameters to config.py.

Ticket

https://www.pivotaltracker.com/story/show/182859513 https://www.pivotaltracker.com/story/show/182406438

Contributions

Most updates were needed to move hardcoded filenames to config.py and import.

• config.py: moved all hardcoded filenames and paths to this location!
• demo_level_feedback.py: there was no way to test regressions on this code, I added a demo to ensure the code still worked.
• demo_rsvp_calibration.py: updated to use init_display_window for easier testing
• matrix/display.py: small fix to opacity reset
• helpers/stimuli.py: remove unneeded stim length check on inquiry generation (this broke matrix on accident)

Test

• make test-all
• Ran all demo code using parameter files
• bcipy with fake data server
• Ran all BciPy registered tasks in fake data mode

Documentation

• Are documentation updates required? In-line, README, or documentation? Verify the updates you did here.

Changelog

• Is the CHANGELOG.md updated with your detailed changes? Not yet