perf_fix

Remove usage of CoreMacOSX.FileManager_findFolder to lookup user's Documents and Desktop folders on Mac. Instead cheat and assume they live under ~/Documents and  ~/Desktop, where we fill in ~ with the value of user.home

I'm doing this because 9 times out of 10 when I launched junit tests in a dev instance, they'd never start, and under the debugger I could see these calls as being locked. I've seen instances of this in the past as well.

I'm putting it up for a PR in case you or anyone else can thinks of a reason why this fix wouldn't work, or would give us the wrong results.