Design an LST-aligned output format

[steven-murray]

To enable the work of @tyler-a-cox and @AaronParsons, we should discuss and implement a way to handle LST-aligned (but not yet averaged) data.

Things to keep in mind are that data reading/writing is expensive, so once we read a bunch of data that is LST-aligned, it might behoove us to do all the operations we want on that data before averaging it and writing out the average.

[steven-murray]

Obviously, this will heavily depend on (or influence) #846