Add additional helper methods to modules

[anthonysena]

          This function is always the same for every study you just need:

• List of targets, list of outcomes, list of negative controls. So we should probably just add a method to the SCCS module to create this list?

createExpsoureOutcomeList(exposureCohortIds, outcomeCohortIds, negativeControlOutcomeIds) {...}|

I think the same can be done for CohortMethod.

This would likely be simpler for users. They can still use the package functions if they wish but making utilities will make their lives easier.

Originally posted by @azimov in #172 (comment)

Additional comments along the same lines:

#172 (comment)
#172 (comment)