load EHR data from a FHIR server

[ebrahimebrahim]

Instead of loading EHR data from local tables, we should be able to type in the address of a FHIR server and load the EHR from that.

• Work on creating the FHIR server is taking place in lungair-fhir-server
• This is linked to introduce an EHR dataset that contains NICU data #23 because the idea of lungair-fhir-server is to serve NICU data selected from MIMIC-III (provided only with credentialed access on PhysioNet).