[Merge] lp:~frank-heimes/installation-guide/ubuntu-18.04-s390x into lp:~ubuntu-core-dev/installation-guide/ubuntu

[Frank Heimes]

Frank Heimes has proposed merging lp:~frank-heimes/installation-guide/ubuntu-18.04-s390x into lp:~ubuntu-core-dev/installation-guide/ubuntu.

Commit message:
adjusted support time, IBM Z/s390x and IBM POWER data

Requested reviews:
  Ubuntu Core Development Team (ubuntu-core-dev)

For more details, see:
https://code.launchpad.net/~frank-heimes/installation-guide/ubuntu-18.04-s390x/+merge/343452

bookinfo.xml added year 2018
what-is-ubuntu.xml adjusted support times
adjusted info on IBM Power and IBM Z and LinuxONE (new family names for s390x)
-- 
Your team Ubuntu Core Development Team is requested to review the proposed merge of lp:~frank-heimes/installation-guide/ubuntu-18.04-s390x into lp:~ubuntu-core-dev/installation-guide/ubuntu.