[Qt] massive options/settings rework (no core changes)

- add new options for database cache and script verification threads
- add label which displays options that are overridden by command-line
  parameters
- proxy settings are not applied on-the-fly anymore and require a client
  restart (ApplyProxySettings() was removed and was not working very well
  anyway)
- re-work options reset and require a client shutdown (as it is much
  easier to do it this way without having to mess with what can be changed
  on-the-fly and what needs a restart anyway)
- options reset now writes default values for every single option
- when changing an option which requires a client restart display a 10
  second warning message in statusLabel (via a QTimer)
- when applying the changes via ok change that to a persistent message,
  which is displayed even after closing optionsdialog and re-open it, when
  no client restart was made
- remove dialog boxes used when changing language or proxy settings
- add setRestartRequired() and isRestartRequired() to OptionsModel and
  use the set function when updating options to signal OptionsDialog
  when a restart is needed
- resize optionsdialog a little and add some min sizes for certain GUI
  elements
- remove apply button from optionsdialog
- save and restore optionsdialog window position
- update nTransactionFee in QSettings with a set -paytxfee value when
  opening optionsdialog (I'm not sure about this yet, perhaps revert to
  not updating QSettings and just display current -paytxfee value in
  optionsdialog.)

src/qt/optionsmodel.h

@@ -34,6 +34,8 @@ public:
         DisplayAddresses,       // bool
         Language,               // QString
         CoinControlFeatures,    // bool
+        ThreadsScriptVerif,     // int
+        DatabaseCache,          // int
         OptionIDRowCount,
     };
 
@@ -41,7 +43,7 @@ public:
     void Reset();
 
     /* Migrate settings from wallet.dat after app initialization */
-    bool Upgrade(); /* returns true if settings upgraded */
+    void Upgrade();
 
     int rowCount(const QModelIndex & parent = QModelIndex()) const;
     QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;
@@ -52,17 +54,24 @@ public:
     bool getMinimizeOnClose() { return fMinimizeOnClose; }
     int getDisplayUnit() { return nDisplayUnit; }
     bool getDisplayAddresses() { return bDisplayAddresses; }
-    QString getLanguage() { return language; }
     bool getProxySettings(QString& proxyIP, quint16 &proxyPort) const;
     bool getCoinControlFeatures() { return fCoinControlFeatures; }
+    const QString& getOverriddenByCommandLine() { return strOverriddenByCommandLine; }
+
+    /* Restart flag helper */
+    void setRestartRequired(bool fRequired);
+    bool isRestartRequired();
 
 private:
-    int nDisplayUnit;
-    bool bDisplayAddresses;
+    /* Qt-only settings */
     bool fMinimizeToTray;
     bool fMinimizeOnClose;
     QString language;
+    int nDisplayUnit;
+    bool bDisplayAddresses;
     bool fCoinControlFeatures;
+    /* settings that were overriden by command-line */
+    QString strOverriddenByCommandLine;
 
 signals:
     void displayUnitChanged(int unit);