Proof of concept: color magnitude diagrams from catalogs in Imviz

[bmorris3]

Description

This proof of concept PR visualizes a linked color magnitude diagram with an image in Imviz. This was developed during the catalog performance hack day.

This was a two hour hack, and many things could be done correctly if we take up this line of work:

• the ImvizScatterViewer was adapted from the LCviz TimeScatterViewer. We could develop a generic one that LCviz inherits.
• the ScatterViewerState is directly copied from LCviz. I would have imported it from LCviz, but LCviz imports jdaviz, so the circular imports made that impossible.
• we need a data translator for an astropy table, which should go upstream in glue astronomy. I made a TableHandler class here by copying and modifying the LCviz glue translator for lightkurve.LightCurve objects, which are ultimately a specific kind of astropy table.

Demo video

...is too big to embed in GitHub, so watch it via Box: https://stsci.box.com/s/9xzt8367nodxvn15oy9ilohpcot8y7xt

The demo notebook used in the video is located in this PR at notebooks/concepts/imviz-catalog-viewer.ipynb.