Refine description of impact profile landing page

I recommend revising the description as follows:

Impact profiles are weather-normalized and scaled hourly profiles that reflect the impact of an energy-efficiency or load-shifting measure on energy usage. They reflect the hourly differences between the usage of the baseline case and the usage of the energy-efficiency or load-shifting measure case during a typical weather year. These hourly differences are scaled by dividing the energy impact in each hour of the year by the total annual energy savings so that the sum of all 8,760 hours equals one.