resolve aliases when browsing in the 3rd pane (by type)
consider resolved aliases in more places
set initial file icons based only on type

Calling `iconForFile:` causes the file's attributes to be read from disk, which could be very slow in some cases, defeating the purpose of `setQuickIcon…`. Instead, we do it in `loadIcon…` which runs in the background.

fixes #1431
add quick icons for folders

They typically don't have an extension, so they need to be handled
separately.
update icons on the main thread

to avoid several attempting to update simultaneously
always call `selectObjectValue:` when the object changes

`setObjectValue:` is lacking some smarts for comparing objects and
managing observers. `selectObjectValue:` takes care of that, as well as
the two lines that were removed.
Merge pull request #1501 from pjrobertson/backgroundTriggers

Respect the 'run tasks in background' setting for triggers as well
Merge pull request #1490 from skurfer/fileIcons

set initial file icons based only on type
Merge pull request #1485 from pjrobertson/aliases

resolve aliases when browsing in the 3rd pane (by type). Fixes #1484
Merge pull request #1508 from pjrobertson/misc

Misc - mainly fixing unit tests. Fixes #1509
add a unit test for URLs ending in `.local`
make sure `.local` is treated as a TLD

(and simplify the script that builds the list)
Merge pull request #1514 from skurfer/localDomain

Include `.local` in the list of top-level domains
update references to hi-res images
set scaling to "Up or Down" for images in the Setup Assistant
Merge pull request #1518 from skurfer/tiff

update references to hi-res images
Merge pull request #1449 from pjrobertson/internalCommands

Add more internal commands for opening prefs. Fixes #1448
make sure 64-bit-only plug-ins require the 64-bit QS
define the compatibility break in a config file for future re-use
update a comment to reflect the generalized approach