Also create an ENTITY for qt5 or qt5-alternate and use that
to specify the qt5 dependenies.
The complete KF5/plasma packages should use the full qt5 build, but
the lxqt kf5/plasma components only need qt5-alternate.
I've had a TODO list item after a Discussion with Bruce about this particular
package since last package freeze. Because of it's reliance on Qt5 and the fact
that it's only used for KHelpCenter, it really does not belong in
General Libraries. Moving it to X Libraries should suffice in this case,
since it doesn't really fit in KF5 either.
In addition, update the dependencies and the installed files list, and
add short descriptions for the two libraries installed by this package.
