pull request... ;)

[Harald Albrecht]

Hi Jean-Baptiste, hi Vincent,

on the basis of the timeline clip corner discussion I've managed to 
teach myself a few new tricks, or rather click and edit around 
satisfyingly. I've added a new timeline config UI option to choose 
between rounded and straight corners, with associated painting code for 
clips and transitions.

Since I don't know how to hand the changes over to you, I'm asking here; 
and I've send a pull request on github to the KDE/Kdenlive repository.

Best regards,
Harald