fd46::/64 is a randomly chosen value within fc00::/16

/reviewed-on nexedi/slapos.package!54

It is important to have them in case of problem analysis.

The most important thing is that Certificate has to match the Key.

The CA certificate is fully optional, so make it seen as this, and also
explain what is its purpose.

The install.sh script has to remove all software releases except the provided
ones, and they are different in various scenarios.

The certificates might be  needed, so ask the user for domain name and
the certificates.

As a "safe" way to transmit the certificate use mktemp.

This functionality requires "playbook: Allow correct certificate with domain"

Thanks to using install.rc it is possible to easily select any playbook
to be used during the installation.

During upgrade process it is requried to stop for some time requesting
of exsiting software releases and remove them from slapproxy.

The ansible, which will run later, will take care of readding new
software release and crontabs.

As the process of installing from ERP5 can be controlled with a script,
create such script instead of many steps.

This script is safe to be run many times.

This is ERP5 Standalone installation (as erp5-standalone script
provides) offline installation.

/reviewed-on nexedi/slapos.package!34