SDD: Add plant report variables

Add report variable for plant outlet node mass flow.
Fix error translating flowrate for plant component setpoint

Fluid flowrates were incorrectly set to autosize even when hard sized
values are available for towers.  This change only pertains to the
component setpoint based operation scheme.
Merge branch '73802200-SDDEnhancements' of https://github.com/NREL/OpenStudio into 73802200-SDDEnhancements