Did a lot of changes here. Login function is finished and programmed.
Now users can login with "user: test, pw: test" for testing purposes.
Employees now have different Privileges for the different tabs in the
software. DatabaseManager now has a performSQL function for all managers
to come. Employee has been changed with a privilege variable in both the
program and the database. Changed name for the TestDatabase class to
AddTestDataToDatabase, since this is really what the class does.