Reduce the finder proxy cache time to 0.5s
Reduce Latest Download cache time

And tidy up file
Set the default proxy cache time to 2s
move the kQSDefaultProxyCacheTime definition to the header

…so other proxy objects can use it
generalize getting info for other proxies
respect the cache time of the passthrough proxy

If there isn’t one, use the default.
adjustments to failDate

* It only gets used in a class method, so it doesn’t need to be an
iVar. It’s declared locally.
* Made it static
* Sync the timeout for failure with the default proxy cache time.
They’re not the same thing, but they should both be updated as hardware
gets faster.
make Current Selection more efficient

* only get information for the current application once
* alter the order when getting types: types from plist, fallback to
string, types from provider → types from provider, types from plist,
fallback to string
* eliminate the poorly named passthroughProxyInfo class method
keep copied QSObjects in memory

The old method would try to pull the object from a specific memory
address, but that address could point to garbage by then.

Also, the result from `objectWithIdentifier:` was never being returned.
Now it will be.

fixes #1716
let QSLibrarian hang onto copied QSObjects
add '(alias)' to the details of file alias objects
Use the file UTI for getting a file obj icon from NSWorkspace
Add the alias (arrow) image overlay to alias object icons
Bring aliases branch in line with master
Switch to using NSURL for finding file attributes
Add an isExecutable method for file QSObjects
Tidy up NSFileManager methods to use NSURL resource keys instead of LSInfoRec
Use Sparkle's auth method for moving restricted files to trash. Fixes #28
Update the results display on the main thread. (Similar to #1655)
store the identifier as the identifier instead of the string value