We don't need two (and half) templating systems anymore, yay!
I'm keeping the changes minimal, to make the diff manageable. Some enhancements
due to a better templating system might be possible in the future.
For handling of '## ' — see the next commit.
They were left from an early review iteration, when hibernate-resume
functionality was intended to work also outside of initramfs.
Now this is not the case, and these dependencies became redundant
as systemd-fsck-root.service can never be part of initramfs, and
systemd-remount-fs.service makes little sense in it.
This can be used to initiate a resume from hibernation by path to a swap
device containing the hibernation image.
The respective templated unit is also added. It is instantiated using
path to the desired resume device.