OpenAPI Validation Fixes

OpenAPI validation seems to have become stricter about checking for None defaults
in parameters that don't allow None. I have
modified two things as a result:

1. StageTypeProperty (used to pick between SangaStage and SangaDeltaStage)
now defaults to SangaStage (which is the
original behaviour anyway)
2. It is now allowed to pass x,y,z=None when making a move - this is the same as
not passing the respective argument, so the
function already correctly handled this case.

openflexure_microscope/config.py

@@ -5,7 +5,6 @@ import os
 import shutil
 from typing import Optional
 
-
 from .json import JSONEncoder
 from .paths import CONFIGURATION_FILE_PATH, SETTINGS_FILE_PATH