Implemented further database functionality

Barkans, Reinisrequested to merge
setting-up-in-memory-db into master
  1. Implemented new Patients and Test Results tables and their methods
  2. Populating the test results table with history.csv
  3. Discharging a patient
  4. Backup method for persisting the in-memory database to disk
  5. Unit tests

Merge request reports