Introducing new image parameter 'upright' and corresponding variable $wgThumbUpright.

Introducing new image parameter 'upright' and corresponding variable $wgThumbUpright.
This allows better proportional view of upright images related to landscape images on a page without nailing the width of upright images to a fix value which makes views for anon unproportional and user preferences useless
Usage:
* [[Image:pix.jpg|thumb|upright|caption]] = Upright image will be scaled down by $wgThumbUpright (default 0.75, seems to me the best value)
* [[Image:pix.jpg|thumb|upright=0.6|caption]] = Upright image will be scaled down by 0.6
Size of thumb is always rounded to full __0 px to avoid odd thumbsizes and spare the cache

If used in combination with a width, upright will be ignored.