This adds the framework for unit testing Moonraker via pytest.
Initally only moonraker.py, klippy_connection.py, and confighelper.py
have acceptable coverage. Coverage for other modules will be added on
an incremental basis, when most of Moonraker's source is covered tests
will be conducted via GitHub actions.
Signed-off-by: Eric Callahan <arksine.code@gmail.com>