Fix and tidy up the OS X app

Redone pull request #613 for rauix to be cleaner. Does not include
spaces-to-tabs or other formatting changes that #613 had.
Merge pull request #631 from portablejim/osx-patch1

Fix and tidy up the OS X app
Merge pull request #630 from Viper-7/master

RFC: Simple resume support for pack downloads
CHANGED: Ignore local/virtual/p2p interfaces when searching for MAC address