Improve logic when zero occupants but kWh/yr specified

[shorowit]

User submitted an HPXML file where there were zero occupants in the dwelling unit but the annual lighting kWh/yr was specified. Currently OS-HPXML will zero out all occupant-based end uses (lighting, most appliances, plug loads, hot water fixtures, etc.). But if the user has explicitly specified the kWh/yr to use, we probably shouldn't override it. The user did not expect to see zero lighting energy use.

If we use interior lighting as an example, the logic could work like this based on the HPXML inputs:

• Default: no energy use if zero occupants
• Lighting fractions: no energy use if zero occupants
• Annual kWh/yr: use specified value regardless of number of occupants

We should also update the documentation to make it clearer that some end uses are zeroed out when there are no occupants.