fully in /opt.
This happens because, similar to lxqt-panel, it doesn't know how to find
the headers in /opt/kf5 and assumes they'll be found in /usr. Work
around this with CXXFLAGS.
Also updated the short description for screengrab itself
There are several packages that are not critical for the lxqt desktop
but are useful. A user can test out lxqt without the packages in apps.
It is useful to have at least one terminal emulator when testing, but
xterm will do.