Fix recent ugly fonts in cs_CZ, hu_HU (bnc#879991).

It seems that Qt picks up random (and worst) fonts when no font is
specified as default.  And libyui-qt doesn't set the font as default,
thus it results in the weird output.
version + changelog
factored out and commented the Sans Serif font
Merge pull request #38 from mvidner/default-font

Fix recent ugly fonts in cs_CZ, hu_HU (bnc#879991).