Correct reheat terminal fixedMinimumAirFlowRate()

AirTerminalSingleDuctVAVReheat_Impl::fixedMinimumAirFlowRate() returned
the wrong value.
SDD: Always use FixedFlowRate for reheat terminal

For AirTerminalSingleDuctVAVReheat always setZoneMinimumAirFlowMethod("FixedFlowRate")
SDD: Remove simple hot water loads

Use a detailed hot water system instead of simple hot water loads.
Previously the potential to have both at the same time existed,
resulting in duplicate loads.
SDD: Update HotWtrHtgRtSim element

Update translator to use new element name HotWtrHtgRtSim instead of
HotWtrHtgRt.
SDD: Update element names for ventilation

FollowAvailability is now FollowHVACAvailability
OACtrl:AvailSchOffsetStart is now OACtrl:StartUpDelay

StartUpDelay is always a positive integer representing the number of
hours to delay ventilation.
Merge branch 'develop' of https://github.com/NREL/OpenStudio into develop