Initial change to isolate Dusk Server setup.
Initial change to isolate Dusk Server setup.

- Originally we used the test class setUp() but this likely includes
  migrations, which we don't want to run in the server process.
- Added a new method to be more explicit with setup, which
  can be overridden as necessary.
- Main requirement is to ensure application environment is consistent
  between the test and the server.

orchestral/testbench-dusk,orchestral/testbench-dusk