added system to applies to of scheduling_Protocol (see errata)
Added Data_Rate_Units to replace Data_Volume_Units (left it in for
compatibility).

Added Data_Rate to communication.
commented on Data_Rate as SAVI specific property.
use the term Data_Rate instead of Data_Volume.
Also for Data_Rate_Units.
cleaned up data rate stuff.
corrected by adding unit to limit.
Added Data_Volume_Units for compatibility.
removed range limit on Data_Rate
Added Data_Rate_Units as constant for property lookup