Support NTFS3 kernel driver

[madsl]

We should support using the in-kernel ntfs3 driver if it exists on the system.

core.py today just run "mount" with no -t -argument when mounting the target. We should check if there's ntfs3 support in the kernel, and if there is, use "-t ntfs3" when mounting. As things are today, you have to provide "-t ntfs3" when mounting ntfs to make the kernel use the new driver.

I wonder if the best way to do it is to check for target fs == NTFS, and then first try ntfs3, and if not working then ntfs as fallback. That way we might be able to load ntfs3 support if it's built as a module. If not, then fallback to fuse/ntfs3g.