Add "retina" styles for high-dpi screens
FIX: Ensure that columns are unique within a gridfield
GridFieldDeleteAction missing button text without icons

The text on the button is hidden from view via CSS already. This allows the button to have text in the event that the GridField does not provide icons (and likely is better for your screen readers).
Merge pull request #3430 from kinglozzer/pulls/retina

Add "retina" graphics for high-dpi screens
Fixing the failure of some tests if the framework dir is named something other than 'framework' (which is a legitimate option)
Merge pull request #3461 from NightJar/testfix

Fix some edgecase test issues