[kdenlive] slowmoVideo installable on Debian 8 and Ubuntu 14+

[Narcis Garcia]

I'm testing this spectacular tool since this week it's packaged for
mentioned distributions:

https://github.com/slowmoVideo/slowmoVideo/issues/46

Massimo Stella suggested to embed slowmoVideo into Kdenlive:
https://kdenlive.org/node/9458

I must warn users that its rendering consumes a spectacular amount of
space (something like 10 temporary PNG files per each frame). And
rendering process can be 4x timeline time in an average PC.