Subarray CTE notebook

[tddesjardins]

Some of the formatting in the subarray CTE notebook needs to be altered. In particular, div alert boxes should be used to warnings and important notes. Also emphasize more strongly to users that they will need to set up JREF to run the example. Add in a table of contents.

[tddesjardins]

In retrospect, I think a table of contents can be left out (they're a headache to do anyway, and they're not automated so they can get out of sync).

Jupyter Lab has no plans to incorporate the bootstrap CSS classes (see marl/jams#183 and jupyterlab/jupyterlab#2693), so div alert boxes are also not necessarily a good plan for cross-compatibility between notebook and lab. Therefore take these out and replace them with an alternative.

The current version of the notebook does have fixes for JREF so anyone can run it without being on the internal STScI network.

Maybe hide some of the astroquery file copying/moving stuff behind and imported function to clean up the examples. Could point users to the calibration workflow notebook that has the more expanded out astroquery code as a demo, and also link them to the astroquery documentation (or the MAST Labs blog?).