pyside2 support

[looooo]

#279

maybe someone can test if this works with pyqt5.
Also this doesn't fully fix the issues I have with pyside2. There is still this problem:

  File "/home/k/conda/envs/freecad-gcc7/lib/python3.7/site-packages/freecad/ipython/init_gui.py", line 35, in <module>
    console = put_ipy(dock_widget, mw)
  File "/home/k/conda/envs/freecad-gcc7/lib/python3.7/site-packages/freecad/ipython/init_gui.py", line 22, in put_ipy
    widget = RichJupyterWidget(parent=parent)
  File "/home/k/conda/envs/freecad-gcc7/lib/python3.7/site-packages/qtconsole/rich_jupyter_widget.py", line 53, in __init__
    super(RichJupyterWidget, self).__init__(*args, **kw)
  File "/home/k/conda/envs/freecad-gcc7/lib/python3.7/site-packages/qtconsole/jupyter_widget.py", line 118, in __init__
    super(JupyterWidget, self).__init__(*args, **kw)
  File "/home/k/conda/envs/freecad-gcc7/lib/python3.7/site-packages/qtconsole/frontend_widget.py", line 182, in __init__
    self._call_tip_widget = CallTipWidget(self._control)
  File "/home/k/conda/envs/freecad-gcc7/lib/python3.7/site-packages/qtconsole/call_tip_widget.py", line 36, in __init__
    QtGui.QStyle.PM_ToolTipLabelFrameWidth, None, self))
RuntimeError: Internal C++ object (PySide2.QtWidgets.QStyle) already deleted.

[ccordoba12]

maybe someone can test if this works with pyqt5.

I don't understand why you can't test it yourself. Please be sure that this doesn't break pyqt5 if you want this merged.

[looooo]

Starting qt-console makes no problems and I guess pyqt5 is used by default.

[looooo]

also starting qtconsole with pyside2 doesn't make any problems (Also without this diff). The problem occurs if I try to embed qtconsole into FreeCAD. So maybe this is more related to freecad. I close this for now.