AROS HD installer ready for testing

The new HD installer is now included on the nightly ISO and is ready for testing. However, there's currently a bug in either Wanderer or FFS that needs to be worked around. After startng the installer, you need to quit Wanderer before continuing (unless you're not going to format any partitions).

Be even more careful than usual with this version of the installer, ie. don't expose a machine with unbacked-up valuable data to it. It should preserve all existing partitions if requested, but no one has tested this so far besides me.