Installation 2.0

[pabera]

• Create verify_file_does_not_contain_string function
• Move code for ipv6 into separate function; allow both enable/disable options
  • Remove IPv6 Disable Support (Do not ask anymore for disabling ipv6. Keeping the function though, but the effect on reducing the boot time is minimal. The function could be offered to users at their own convenience.)
    • Fix for nginx with disabled ipv6 #2254
    • Nginx failing to start for non ipv6 setup #1889
• Move code for static_ip into separate function; allow both enable/disable options, allow to set specific IP
  • Should use NetworkManager
• Move code for boot_screen into separate function; allow both enable/disable options
• make ssh_qos.sh an option (removed from main installation); allow both enable/disable options
• Move "Disable On-chip audio" to be self-service. it will not be a question in the installation anymore
• introduce "Optimized Defaults": This means we will set some opinionated system settings without asking the user. Documentation explains how to influence them afterwards.

... more will be added

[s-martin]

Coming from this comment #2313 (comment) I suggest the following addition:

Have a module/script, where all commands are collected which should bring the box in a defined state.
This should be used also for upgrade paths, where we would remove previously used items (e.g. uninstall RPi.GPIO if we follow the solution in #2313).