Incorporate Bayesian measurement error procedure into estimateCellCounts

[sandrews5]

New functionality to estimateCellCounts that will allow for eosinophil estimation in cord blood using the adult blood reference panel. Can be extended for additional cell types in the future.

[kasperdanielhansen]

I don't understand why there are no updates to the documentation besides a new reference. The code suggests that you're automatically doing Bayes estimation under a certain scenario. I would at a minimum expect documentation updates explaining what is happening, and I would also have expected that this could be forced-enabled/disabled by setting an option to estimateCellCounts().

[sandrews5]

Thanks for the suggestions Kasper. I've added a new argument to estimateCellCounts so that the user can turn off this behavior if needed. And I've also added a short little paragraph to better explain when the function invokes the measurement error procedure.