add retina icons
replace NSMakeSize() with pre-defined QSSizes
replace hard-coded sizes with QSMaxIconSize

…in places where it makes sense to do so.
allow for 256x256 icon representations
get the max icon size from the active interface

fixes #1044

Previously, it would stay at the default 128x128 unless you manually
changed the interface after every launch.
make some hard-coded values relative

Some of the code seems to have been based on the assumption that max
icon size will always be 128 x 128.
trigger window icons should be hard-coded to 128x128
avoid a notification and call interfaceChanged directly
remove calls to createIconRepresentations and createRepresentationOfSize:

These shouldn't be necessary any more.
retain quality for shrunken images

and remove unnecessary code to create a specific representation
remove duplicate definition of QSMaxIconSize
ignore interface icon size, start big and let NSImage do the right thing

The QSMaxIconSize should only apply to the main interface, not all these other contexts.
set image scaling for QSObjectCell
use a copy of the find icon

makes sure this method has exclusive control of the image's size
use an image well for the unsure quit dialog
Quit confirm window tweaks

* balance space above and below the content
* remove the titlebar
* center the window with NIB settings
* change deployment target to 10.6
quit confirmation fixes

* make sure everything refuses first responder
* cast the window to QSBorderlessWindow
* remove unnecessary code
Merge pull request #1378 from skurfer/retina

Retina support