The kde-env-user stuff is probably extraneous, users who will go through and
tweak the installed kde-env-master.sh script should be skilled enough to
already have their own .bashrc (or equivalent) and be able to setup their own
env vars prior to sourcing kde-env-master.sh

This also ports some of the Qt4/KDE4 stuff to Qt5/KF5, removes now-unnecessary
environment variable settings, etc.