Update killed retina support

Now I always have to set the zoom level to 50% on my retina screen. Worked in previous versions. Saving permissions to browse all directories does not work anymore as well.

Update:
Now scrolling performance while image is zoomed in seems to be worse as well. Delays and lags everywhere on a Mid 2015 15" Macbook Pro with 2.8 GHz i7 + AMD Radeon GPU

duongel about Xee³: Image Viewer and Browser, v3.5.2