Clean up format list output a bit

Cleaned up the format list display a bit (not sure I got it completely
right).
Rearranged the DASH formats to be grouped by type rather than container
for easy reference.
Corrected format 171 being listed as 48 Kbit (real value 128)
Cleaned up some typos
[youtube] Warn user if DASH offers higher quality

Check to see if there are 1080p or higher DASH formats available, and
warn the user that they're not getting the highest quality. Partially
broken in that it assumes 720p will always be the highest available mp4,
but I need sleep.

As I was writing this commit message, I only just now realized this will
display even if the user does request a DASH format. I need to stop
coding after 3 AM.