New compatibility for Salome 9, with python 2+3 support

[meritzio]

The new major version of Salome 9 has now adopted the use of python3 for its scripting. Old python 2 methodology such as the print function being used without calling brackets has now been removed and meant that the script would no longer run in Salome 9. I have implemented python 2/3 compatibility to handle such issues.

• print has been applied for both python 2 and 3 to feature calling brackets. print 'hello' -> print('hello')
• The deprecation of xrange in python3 has been replaced with range in python3. This does not affect performance.
• Salome 9 no longer accepts arguments in updating the object browser. salome.sg.updateObjBrowser(1) -> salome.sg.updateObjBrowser()

I have tested the script on Salome major versions 8 and 9 and seen no issue with the script.

Additionally I have made the source code more pythonic and added a reference to the source code repository within the polyMesh headers so that users can easily check for script updates.

[meritzio]

I hope you are doing well Nicolas!

One thing I might look at soon with this script, given that python 3 has better support for binary data, is adding an option to export binary polyMeshes. I think this would improve writing speed somewhat and reduce polyMesh file sizes significantly.