update konversation docbook to kf5

remove kappname + package, no longer used
use entities from kdoctools (url, mime)
bump date + releaseinfo
replace &kde; with &Qt; and &kf5-full; and &plasma;
fix wrong links
fix changed gui strings
cleanup/fix scripts
replace common menu items with link to fundamentals
imported a few usefull faq's from userbase
remove obsolet appendix installation
update screenshots
add link to Scripting guide on Userbase
comment commands mail + sayclip
Differential Revision: https://phabricator.kde.org/D3556