New function to get properties from an image

Will replace the old function
Add param to file url

needed to get file size
Clean code / add titlebar infos

The titlebar of the preview window now display things like that :
WIDTHxHEIGHT | filename | filesize

If the image is bigger than your screen size, the dimensions displayed at the bottom of the window will be shrinked proportionally (like the image).
I'm currently searching for a solution.. It seems impossible to get the screen size in a QuickLook plugin via NSScreen or Quartz API...
A solution could be to force the size of the preview window, but for big resolutions (retina / iMac 27") it will not be optimal..