- Added channel identification by ``tiskitpy_id``, which includes cleaning
information.
The ``tiskitpy_id`` for uncleaned data is the ``seed_id``.
- Added class CleanedStream and revised the guts of several classes, including
renaming ``SpectralDensity.channel_names`` to ``SpectralDensity.ids``.
- CleanRotator class now has a property `variance_reduction` which gives the
variance reduction obtained during __init__()
- Added `SpectralDensity.plots()` and `.plots_coherences()`, to compare
multiple `SpectralDensity` objects