Conditional plotting of read length distributions vs. a summary table

The mhpl8r pipe report includes a module for plotting read length distributions.

Screen Shot 2022-06-17 at 2 42 48 PM

However, when all samples have uniform read lengths, you end up with something like...this.

Screen Shot 2022-06-17 at 2 42 55 PM

This PR replaces these plots with a table of read lengths, when and only when all samples have uniform lengths.

Screen Shot 2022-06-17 at 2 43 03 PM

Closes #137.

[x] Changes are clearly described above
[x] Any relevant issue threads are referenced in the description
[x] Any new features are tested (see the development manual for details)
[x] CLI documentation (see docs/cli.md) and Python API documentation (see microhapulator/api.py) are up-to-date and in sync
[x] Substantial changes are documented in CHANGELOG.md (see https://keepachangelog.com/en/1.0.0/)

bioforensics / MicroHapulator