Update + fix ark docbook

remove obsolete FIXME about Passwords
Delete <appendix id="installation"> and move para about requirements into <chapter id="introduction">
Reason for deleting the appendix see: https://git.reviewboard.kde.org/r/124167/diff/3#1
Add missing word "menu"
Fix wrong markup (guimenuitem -> guilabel)
Fix wrong shortcut
Remove <email> markup, where it is already part of the *.mail entities
REVIEW:127521