Add a new Totem plugin to transcode videos

[thibaut bethune <thibaut bethune gmail com>]

I really like Totem : simple but powerful  (YouTube plugin since
version 2.22, create DVD plugin since version 2.26, new resume
functionality in version 2.28...)

Maybe that Totem could also have a plugin to transcode videos :
creating a DVD video is not the only way today to carry away videos

It could rely on another simple tool like Transmageddon (or Arista) for instance

Thanks