Revisit HPXML header inputs for whole MF building modeling

[shorowit]

Certain inputs get stored in the HPXML header -- i.e., outside of the individual Building elements. Now that we're going to allow modeling whole MF buildings, that means we can't vary those inputs for each Building (dwelling unit).

We should review those inputs and see which should be moved into the individual Building elements so they can vary across dwelling units. For example, simulation control settings (run period, timestep, etc.) should stay where they are, but most everything else should move.