[Function] CreateVariable [Arguments] variableName, value(optional), scopeName(optional) [Return Value] Success or Error [Description] 
Creates a variable. If scopeName is not specified, the variable is created in the top most scope on the scope stack. If no value is provided, the variable is created with the default value specified by the underlying datamodel. A Failure status is returned if a variable of the same name already exists in the specified scope.