update imported kcm docbooks to kf5

add kcm docbboks and the konqueror docbook to the build system
rename subdir kcontrol to kcontrol5 and adapt X-DocPath entries to install the kcm docbooks in subdir kcontrol5 to be co-installable
update dtd
bump date + releaseinfo
proofread + update

@david Faure:
the konqueror repo has three additional desktop files (kcmcss.desktop, fileappearance.desktop, webappearance.desktop, webbehavior.desktop)
with a X-DocPath entry, but these files are not installed and unsued?
Differential Revision: https://phabricator.kde.org/D3310