bring back width and height to the html img tag

I use a masonry grid for my photographs on my website, but this needs to know the exact width and height of the thumbnail to layout. The old thumb plugin wrote these properties to the returned img tag, the new kirby 2 version doesn´t.

Please bring these back. I don´t know how to get the same properties in that img tag without this modification.

And: I thinks it´s better to write the original picture name to the alt tag by default, than the name of the thumbnail.