spiral_2D_array now uses the center parameter

[robrui]

The spiral_2D_array function accepted a center parameter but didn't use it — the array was always returned at the origin. All other array generators (linear_2D_array, circular_2D_array, poisson_2D_array) add the center offset correctly, so this brings the spiral function in line.

Fixes #413.

• Are there docstrings ? Do they follow the numpydoc style ?
• Have you run the tests by doing nosetests or py.test at the root of the repo ?
• Have you checked that the doc builds properly and that any new file has been added to the repo ? How to do that is covered in the documentation.
• Is there a unit test for the proposed code modification ? If the PR addresses an issue, the test should make sure the issue is fixed.
• Last but not least, did you document the proposed change in the CHANGELOG file ? It should go under "Unreleased".

[fakufaku]

Thanks for contributing! 🤗

[robrui]

Quick note on the CI failures — all 46 failing tests are in tests/directivities/ and trace back to a 403 from sofacoustics.org:

urllib.error.URLError: <urlopen error Failed to download http://sofacoustics.org/data/database/mit/mit_kemar_large_pinna.sofa>

The whole domain is returning 403, even the homepage. So unrelated to the spiral changes here. Might resolve on its own once the server is back up.

[fakufaku]

Thanks for following up. Your test is passing so I'll merge it and fix the CI later. 👍