Overlay configuration normalization

[itlackey]

The properties over the patient and medical facility overlays should match. For example, the type and cohort properties could both be renamed to category. We should also add support for opacity and z-order to the medical facility overlays to bring parody between the two features. I feel doing this will make it easier for others to deploy and configure the application.

We should also consider renaming the "patients" property of "overlays" to "cohorts" to be more consistent with the data schema.