Inconsistent {{.Home}} and {{.User}} values between guest and host templates

In the host templates `{{.Home}}` is the host home directory, and in the guest templates it is the guest home directory.

But `{{.User}}` is always the host user, and not the guest user, which a guest template will have to construct via `{{.User}}.linux`.

I think the guest templates should have additional variables both for the guest user, and for the host home directory.

I don't have a good suggestion how to deal with naming that doesn't require changing the definition of `{{.User}}` in the guest templates, which I don't want to do because it breaks compatibility.

What do people think about this:

Variable | Host | Guest
--- | --- | ---
.User | jan | jan
.Home | /Users/jan | /home/jan.linux
.Guest.User | jan.linux | jan.linux
.Guest.Home | /home/jan.linux | /home/jan.linux
.Host.User | jan | jan
.Host.Home | /Users/jan | /Users/jan

I think the `{{.Guest.*}}` settings are probably never going to be used in host templates, but it doesn't hurt to include them.