default max cam resolution should be less

[Alexey Fisher <bug-track fisher-privat net>]

Hallo all,

i get some time to paly with cheese again. Great app :D but still need
some love.

Now to the problem:
most new webcam have big resolution, and it looks like it is much bigger
than not too old hardware can encode video in realtime. Even my not
really bad CPU (Intel Core2Duo E8400 @ 3.00GHz) can't handle resolution
at 1600x1200 provided by my cam. This CPU can handle simple encoding
with 960x720, but can't do it with some effects enabled. And only at
320x240 it work with effects OK.
The situation with netbooks (athom inside) is worse.

I see, it is not really easy to make right choice, what resolution to
push. What do you thing about this? Is it possible to do some bench test
on first start and write it in config? Or use cpu profile based on speed
and instruction set? Any other ideas?

Regards,
	Alexey