Add polling for admin patient count.

This adds the ability for users to have a more up-to-date representation of how many patients are in the database. This is a working version however it does not do any sort of smart polling, however smart polling can be added if it is determined it is needed.
If you do it as a `member` route then yes, but `collection` operates on all patients, not on a particular patient, and doesn't require an ID.