Allow --format fallback to worst and best

[phihag]

One should be able to specify formats like

45/mp4/best (i.e. pick 45, mp4 (for, say, blip.tv) if it's not available, the best format).

Format selection code should also be generalized for non-youtube IEs.

[Hellmark]

I'd love something like this. Right now, I'm downloading some videos from a youtube channel, and I gotta make one pass from them in my preferred format code, make another pass with no overwrite and my second preferred format code, etc. If I could just be like "--format mp4", and it just grabs the best quality available of, all would be good. Even if I could be like "--format 22/18", I'd be happy.

[phihag]

For youtube downloads, you can already do that, with the exact arguments ("--format 22/18) you mentioned. This issue is just open since this feature has to be generalized across all information extractors (i.e. sites).

[phihag]

On second thought, most IEs just support one format now anyways. Closing this issue for now to avoid further misconceptions.

[Hellmark]

I would like one thing to come of this. Could the manpage be tweaked to clarify the ability to specify multiple options? I tried reading through the docs first, but didn't know of it. Better fleshed out man pages help avoid confusions.