Avoid use of string literal 'NONE', as it can confuse true/false tests #506
Description
configRule.yaml (and all the CFT YAMLs) defaults to use "NONE" for certain parameter values (eg. SourceEvents and SourcePeriodic). This behavior is unintuitive and should be replaced by falsy values for when these values are not defined.
This will also require some updates to rdk.py