Wrote some basic "test-y" plot refactor tests.
Separated out all the tests, added placeholders for 'new' plots.
Added a test for ONCvar 8 (has flagged data) and named the rest ONCvar 1.
Added tests 6 and 7: periodic stuff.
Shuffled the order of the tests; added one for better coverage.
Added 'plot4', currently just an EXPERIMENT to see if we can separate these things out into a data Object and a plotter function.

I'll probably want to futher alter this so that the data object has METHODS rather than a bunch of predefined code that just runs in the __init__ step. Then you could even ASK for which data you want and how you want it to be sliced according to flags, colors, timestamps, etc!
Continuing to refactor code. Next up: putting code into attributes.
Refactoring continues!

* StarData.get_columns() is now in effect
* lightcurve_axes_with_info() is now called within basic_lightcurve!
Removed a lot of the static code in StarData!
More beautiful refactoring.

In StarData, I wrote:
* get_colormag_columns
* get_colorcolor_columns

and the functions
* colormag_axes
* colorcolor_axes
Removed commented-out cruft, added in a couple kwargs.
Reimagined how date_offset works; cleaned up a lot.
Wrote a functioning `multi_lightcurve` code -- proof of concept.
Removed some whitespace in the imports of spread3. Super minor.
Improved/fixed multi_lightcurve, added more documentation overall.