Use native bindings instead of zfs command

[mikroskeem]

Currently volumes are managed using a library what uses zfs command internally. While that works in machines where every single component of ZFS is installed, then it does not work in custom stripped down environments.

There are few candidates for replacing that, but I'm not entirely sure what's their current state and if they are viable for long-term usage:

1. lorenz/go-zfs
2. bicomsystems/go-libzfs (but https://github.com/bicomsystems/go-libzfs/issues/22)