Add several macOS (non-) default application locs

[JayBrown]

Hope this isn't too much. Please see the in-code notes especially about /System/Library/CoreServices. There are lot of non-application bundles in there.

~/Applications
~/Developer/Applications
/Network/Applications
/Network/Developer/Applications
---
/System/Library/CoreServices # incl. ./Applications
/Applications/Xcode.app/Contents/Developer/Applications
~/Library/Developer/Xcode/DerivedData
/Users/Shared/Applications

Note: I'm not sure if passing the absolute POSIX path like that is OK in Swift; cf. e.g. /Developer/Applications. EDIT: fixed with third commit, but some trailing slashes are missing from paths output.

[zenangst]

@JayBrown I think it looks solid. However, we need to make some additional changes after this gets merged. Mainly need to handle apps that are agents. I would also exclude apps that lack an icon (that would get rid of some of the applications that shouldn't show up in the list.

But that is beyond scope of this PR. Great job @JayBrown 🥂

[JayBrown]

Yes, definitely. I think that /System/Library/CoreServices/Applications should be safe, though, because Apple wouldn't call it "Applications", if there was anything other than real application-bundles in there.

As for the parent dir CoreServices, yes, a lot of stuff in there must be excluded: exlude everything that doesn't end on .app; exclude no-icon apps, but we'd have to keep in mind that there are also some regular applications in the default locations that don't have icons, so that rule should imho only apply to CoreServices; exclude agent applications would probably mean those with LSUIElement set to BOOL 1, right? But some of them might still be full-fledged apps, so maybe you can approach this on a case-by-case basis. But generally, I assume, Gray could work with several of the .app bundles in there, not just with Finder.