[Qt] tweak new peers tab in console window

- remove starting height as table header and replace with ping time
- remove columnResizingFixer
- add local address (if available) in detailed node view (on top of the
  right view below the remote address)
- remove some .c_str() by using QString::fromStdString()
- rename Address to Address/Hostname
- rename secs to just s for ping time
- use MODEL_UPDATE_DELAY from guiconstants.h for the peer refresh time
- make PeerTableModel::columnCount() return no hard-coded value
- remove and cleanup dup private: section in RPCConsole header
- add new defaults for column sizes
- remove behaviour which keeps disconnected peers selected and also remove
  code which keeps track of last selected peer stats
- add sync height to detail view
- add some additional NULL pointer checks for clientModel in
  rpcconsole.cpp

src/qt/guiutil.cpp

@@ -804,4 +804,9 @@ QString formatServicesStr(uint64_t mask)
         return QObject::tr("None");
 }
 
+QString formatPingTime(double dPingTime)
+{
+    return dPingTime == 0 ? QObject::tr("N/A") : QString(QObject::tr("%1 s")).arg(QString::number(dPingTime, 'f', 3));
+}
+
 } // namespace GUIUtil