Fixes and improvements for shotdetect

I've commited 4 changes to Johan's git head:

1) Fixed commandline version and comments. Translated some comments from French to English.
2) Updated program version and credits.
3) Changed default threshold from 60 to 75, based on long-term observations of several hundred videos.
4) Added new option: Embed video timecode in graph images.

I'd be honored if you could find these changes useful.