This change improves the layout of the font hinting sub-dialogue of this KCM. Previously there was no spacing around or between the GUI elements and the combo boxes did not line up:

Now the dialogue uses a QFormLayout (but left aligned as discussed in D2853) with style default spacing:

In addition some porting away from KDE4 support is done:

KDialog -> QDialog
KApplication -> QApplication
KProcess -> QProcess
KStandardDirs -> KSharedConfig
KDoubleNumInput -> QDoubleSpinBox

There is, however, some KDE4 porting still remaining to be done, since I'm not sure whether there are Frameworks equivalents to these at the moment:

KGlobalSettings::emitChange(KGlobalSettings::FontChanged);
KFontDialog::getFontDiff()

Built plasma-desktop with these changes, checked correct appearance and operation of Fonts KCM.