Qt methods not wrapped correctly

[jhlegarreta]

Qt methods are not being wrapped correctly or the wrapping libraries are being loaded in the extension, since Qt properties and public slots are not available in Python.

This is verified when trying to invoke such ivars for the qSlicerTractographyDisplayModuleWidget class in a Python script, e.g.

(...)
# Download and load the data
(...)

m = slicer.util.mainWindow()
m.moduleSelector().selectModule("TractographyDisplay")
display_widget = slicer.util.findChildren(name="qSlicerTractographyDisplayModuleWidget")[0]
opacity = display_widget.opacity()

which yields

AttributeError: qSlicerTractographyDisplayWidget has no attribute named 'opacity'

Being able to write a Python script (test) for that class would potentially avoid regressions in that class (e.g. #229). Although a C++ test could be an option, the test data would need to be stored somewhere and be made available for the test; in Python, this task is done without requiring any additional work through the SampleData::downloadFromURL method.

A thread had been started on 3D Slicer's discourse: https://discourse.slicer.org/t/call-a-widgets-methods-in-python/33416/4

[jhlegarreta]

Cross-referencing PR #233.