CEDARS & CET calculations: Add documentation

As a PA,

I want the documentation for formulas utilized throughout the CEDARS site and CET to be updated and published to CEDARS

So that users have the most up to date formula information available.

Identified and requested by SDGE

Per 10/3 ADP meeting -

• It’s putting in clearer language for all the formulas and what calculates all

  the different fields in CEDARS so that you can trace back and somebody who doesn't have a mathematics background can figure out what the calculation is.

• Also to include a formalized CET reference document that is up to date and again, includes the calculations, etc.