Props/gui stuff moved into a separate git repository

fsl/gui/__init__.py

fsl/gui/elistbox.py

fsl/gui/floatslider.py

fsl/gui/notebook.py

fsl/gui/numberdialog.py

fsl/gui/rangeslider.py

fsl/props/__init__.py

fsl/props/build.py

fsl/props/cli.py

fsl/props/properties.py

fsl/props/properties_types.py

fsl/props/properties_value.py

fsl/props/widgets.py

fsl/props/widgets_bounds.py

fsl/props/widgets_list.py

fsl/props/widgets_number.py

fsl/props/widgets_point.py