Add Documentation for Loadshape tool

There are some new documentation and review requirements from today's Loadshape call:

• where and how the Impact Profile ID is created;

• how the avoided-cost combination is generated from the impact profile;

• how the impact profile / avoided-cost combination is mapped back to eTRM permutations;

• what fields are passed from CEDARS/eTRM into CET;

• how accelerated replacement / dual-baseline cases are handled or excluded.

@Sonja, if this already exists, we can compile with the rest of the docx.  Otherwise, will someone tell me who is responsible for adding the documentation?