[mythtv] Preview images in mythweb

[Chris Petersen]

> Any chance the compression ratio might be parameterizable, too?  (When
> you've got 3 or 400 programs on that page, every byte counts, even at
> 100BaseT :-)

They come straight from the backend.  I'd *love* to get an API where I 
can request a specific image size/compression.  Until then, I get what 
the backend sends.  I won't add an imagemagick/convert requirement to 
mythweb because I don't want to deal with the confusion that'll happen 
when people have trouble installing it.

-Chris