a patch needed for QtAwesome : spyder-ide/qtawesome#84

lot of patching to move Guidata to QtPy. And also in testing part, so the external API part.... maybe it's more a new package.

Yet it roughly works, PySide2 bug aside.

replacing classic guidata/Qt per Qtpy is not good:

• the API is changed,
• guiqwt and user codes that depend on it are broken,
• lot of time spent rewriting examples.

the good method would be to move 'vendored' QtPy aside, then redirect guidata/Qt load to guidata/Qtpy Loads.

Benefit = having guiqwt working for free, no more example rewrite

procedure of next test:

• copy guidata sub-directory "qt" as "qt_old",
• copy "qtpy" directory package as guidata package subdirectory "qtpy"
• rewrite guidata/qt as redirection to guidata/qtpy ( from ..qtpy import blabla)
• from guidata import tests; tests.run()

so in second example, we need to patch in the applicative part the ToPyDateTime() and ToPyDate(), that are both ToPython() in PySide2, in guidata/datasets/qtitemwidgets.py

       try:
            return self.dateedit.date().toPyDate()
        except:
            return self.dateedit.dateTime().toPython()

       try:
            return self.dateedit.date().toPyDateTime()
        except:
            return self.dateedit.dateTime().toPython()

I have a mysterious message "Qpicture: invalid format version 0""

but overal, it works without effort (probably not optimal in perf, but I don't care)