Deprecate vtkOggTheoraWriter?

Hi all,

The upstream theora project is alas moribund. I propose therefore that vtkOggTheoraWriter be deprecated:

In the MR, reviewers suggested that I bring it up here on discourse too to get wider attention.



Note that without this, the PyPI wheels will have no way to save movies (other than on Windows).

libvpx may be a potential open-source replacement. It can write .webm video files - playable by vlc, firefox, chrome and safari