Fedora support

[pepawel]

Cryptreboot doesn't currently support Fedora.

It's because:

• Fedora doesn't have unmkinitramfs (lsinitrd has to be used until Ruby implementation is built, which should improve compatibility across distributions and improve performance of lz4 check)
• Fedora's initramfs stores crypttab in /etc (Debian's initramfs-tools use /cryptroot instead)
• even after fixing above, initramfs hangs for a few minutes and requires intervention to boot (entering the emergency shell and quiting it immediately works) - research needed