Frontend support is desired, but current option set is too weak to cover
even simple cases.

Also, fix frontend request.

Minimal change, just made to listen identically on IPv4 and IPv6 addresses.
Settings are identical across all IPs.

It is useful to temporary enable such settings while preparing an instance.

This follows up commit 04ff4930

It prevents data loss while upgrading partition.

Because new s.r.templare requires new Jinja2.

Before, a random password was generated for each group of zopes.

Add a way to takeover remotely.

Why having wrappers of wrappers of wrappers, when we can have simple, readable code?