## Add a GroupFiles button to File Dialog

A new button has been added to the File Dialog, top right corner.
This button allows to enable/disable the GroupFiles feature that group
sequenced file together into a group, instead of always being active eg:

- file_1.vtk
- file_2.vtk

Would be grouped into:

- file..vtk

Now, this feature can be enabled/disabled with this button.
The state of the button is saved in the settings when closing the dialog and ParaView.
