Draft: ZFS support

Add support for using ZFS clones for chroots. I use this with my modified version of the AUR clean-chroot-manager to build packages for my local repo. I don't use archbuild or makerepropkg but my modified version of clean-chroot-manager contains equivalent code to delete the chroots.

Shouldn't change anything if used on a non-ZFS system. zfs-utils doesn't need to be added to the optional depends for the devtools package, since it is a hard dependency for the ZFS kernel module.

Also contains some small typo fixes and TAB cleanups.