VBoxKEXTs/postflight: Remove old kernel extensions so they don't cause trouble on Mavericks.

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.

Moved the kernel extension from /Library/Extensions to /Library/Application Support/VirtualBox to work around new signing requirements for kexts in that directory in 10.9.

Arg!! Remove tiger extensions did not mean remove the "set -e" statement (r62037).

Installer-OSX: change headers

export darwin installer to OSE