isSurveyActive uses a helper function called _isSurveyInPeriodStates.
isSurveyActive uses a helper function called _isSurveyInPeriodStates.

The new function allows to specify more than one period states. It is thus more versatile and will be reused for other public functions.

rhyolight/nupic.son,rhyolight/nupic.son,rhyolight/nupic.son