Notebook for panel design

[standage]

The best place to put code related to panel definition/design (MicroHapDB core code, MicroHapulator core code, or ancillary code) has been a subject of frequent consideration over the last few months. See #66, #67, https://github.com/bioforensics/MicroHapDB/pull/34, https://github.com/bioforensics/MicroHapDB/pull/35, https://github.com/bioforensics/MicroHapDB/pull/36.

This update moves some of the preliminary panel design code out of the MicroHapulator core into a dedicated notebook. Various tests were updated to not rely on these panel definitions being in the MicroHapulator core code.

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• [x] Changes are clearly described above
• [x] Any relevant issue threads are referenced in the description
• [x] Any new features are tested (see docs/DEVEL.md for details)
• [x] Substantial changes are documented in CHANGELOG.md (see https://keepachangelog.com/en/1.0.0/)

[standage]

The test currently failing will be fixed in #75.