user avatar and imagecache_profiles

I've created a fix for this, but its a little messy and could be improved. But it does work.

Key things:
* requires imagecache_profiles to be enabled
* uses the 'Profile picture preset' in the user settings

Works for me on the latest version, but it shoehorned with the avatar selection module right after it. if I spent more time, I could probably rewrite the whole avatar section, but just didn't want to do that.. so you'll see a bunch of 'if $avatar_selection_url || module_exists('imagecache_profiles') cases so the default picture doesn't overwrite the url at the top of the avatar code.

Works on the latest 6.x-20-beta12

Unfortunately alot of the avatar code seems to have changed in RC. The patch can't be applied. I think this would be a great addition to this module, since phpbb doesn't have automatic resizing.

Adding todo tag.