Also fix the name of certain functions.
Do not import `DraftFillet` any more as it's just kept
for compatibility purposes.
Do not test OCA nor AirfoilDAT as it's very improbable
that these formats will gain more support any time soon.
Those unit tests that are registered in `Init.py` will always run,
while those that are registerd in `InitGui.py` will only run
when the graphical interface is available.
This allows us to more clearly distinguish functions that
should be able to run always, from those that may run only
when the interfce is available.
