Installer/darwin: Can't switch between x86 and amd64 binaries with new signing (and we no longer need to).

Installer/darwin: 'ln -vh' => '/bin/ln -vh' -- see public ticket 12275

Installer: Whitespace and svn:keywords cleanups by scm.

Replaced VBoxStartupItems with a launch script and plist located in the VBoxKEXTs pacakge. To provide a script for loading, loading and reloading drivers manually, I modified the existing startup item script instead of cleanup up the intendation of the proposed vbox kext keeper script.