Fixes#130
This should fix pretty much all cases where spaces or other special
characters would break disko due to improper quoting. I searched for all
instances of '.label', '.device' and '.name', so I believe I caught
whatever I could.
In some cases I changed single quotes to double quotes for consistency.
I know we don't usually fix bugs in the legacy table type, but it was so
easy I couldn't resist.
Some users will have `boot.zfs.forceImportRoot = false;` in their
configurations which conflicts with `boot.zfs.forceImportAll = true;`,
so we set it to `true` to match.
As `makeDiskImages` always requires a NixOS configuration, we can
simplify the code by convering it into a NixOS module. Then we can make
it responsible for populating `system.build.diskoImages` and
`system.build.diskoImagesScript`.
