load per-language font info and refresh widget fonts (bnc #866705)

The background (long story):

One problem is that Qt5 doesn't seem to refresh its font database after the
initialization. YaST tries to fetch (or copy) the needed fonts on the fly
(e.g. ipag.ttf for Japanese) to /usr/share/fonts/truetype. libyui-qt calls
FcInitReinitialize() for refreshing fontconfig side, but it doesn't suffice.

This problem of Qt has existed since ages ago, and this seems inherited still
to Qt5. For working around it, YaST introduced lang_fonts setup. This
contains the explicit font list for each language.

That worked with Qt4, but no longer with Qt5, unfortunately.

How to trigger the fontdata base refresh in Qt5: You can load a
font manually via QFontDatabase::addApplicationFont(). Note that you have to
pass a font file path. In the case of Japanese, for example, it'd be like:

    QFontDatabase::addApplicationFont("/usr/share/fonts/truetype/ipag.ttf");

So,instead of (or in addition to) FcInitReinitialize() call in
YQApplication::setLangFonts(), we need to call of such in addition.
In that function, the font fresh is performed only when the font family is
changed. The logic has to be changed, and also we have to give some list of
the newly added fonts there.
release 2.46.9