Add progress of getCohortSequence for multiple ingredients/markers? and maybe for getSequenceRatio too?

[daniellenewby]

It would be useful to provide output of progress when a user is running multiple ingredients/disease cohorts when running CohortSymmetry::getCohortSequence

So when i am running one index against 20 markers it should print out 1 out 20 getting cohort sequence

Not sure if this is also linked to this issue here #97

@xihang-chen