Add Http service class to /services directory.

[sam3365]

Add Http plumbing to the project.

[sam3365]

Coded data.service.ts and subject-data-service.service.ts.
Implemented queryparams devmode and subject.
Ngrx state populated with devmode and subject

[sam3365]

Added devmode and subject querystring parameters. Example:

http://localhost:4200/?devmode=true

http://localhost:4200/?subject=cc-pat-betsy

Using the devmode querystring parameter will result in the devmode button appearing on the bottom right of the toolbar. When you click that, the devmode component will display where you can select a test patient. Upon selection, the patient will be loaded into the NgRx state via a call to the api layer to retrieve the patient profile.

Using the subject querystring will cause the patient referenced by the subject parameter to be immediately loaded into NgRx state. The api layer will be accessed, passing the subject querystring parameter, which is the fhirid of the patient.