Mock datasets for MPoL tutorials and tests

<p>`*.npz` and `*.asdf` files&nbsp;containing visibilities are in the TMS format (opposite that of CASA).</p> <p>logo_cube.noise.npz visibilities have been rescaled such that&nbsp;data - model / sigma follows the expected Gaussian envelope.</p> <p>HD 143006 continuum visibilities have flagged outliers removed and weights rescaled such that the data - model / sigma follows the expected Gaussian envelope, for each spectral window.</p> <p>AS 209 continuum visibilities have been averaged across frequency and have their weights rescaled such that&nbsp;the data - model / sigma follows the expected Gaussian envelope, for each spectral window.</p>