Port and update the Konqueror settings

kDebug(), qDebug() -> qCDebug() with logging category
No need to link with KDELibs4Support
Use Qt5 signal connection syntax
Remove konq/kcustommenueditor.*, no longer used and needs Qt3Support
Convert deprecated What's This -> tool tips
Remove konqhtml/pluginopts.* and associated, Netscape plugins not supported since KDE3
Remove konqhtml/khttpoptdlg.*, no longer supported or accessible from GUI
KDialog -> QDialog
QObject::blockSignals() -> QSignalBlocker
KCModule::changed() -> markAsChanged()
Make the adblock import/export help appear again
KFileDialog -> QFileDialog
KIntSpinBox -> QSpinBox