qt: Add option to (not) spend unconfirmed change

- Add a wallet tab to options dialog
- Move fee setting to wallet tab
- Add new setting to set -nospendzeroconfchange from UI

src/qt/optionsmodel.h

@@ -40,6 +40,7 @@ public:
         CoinControlFeatures,    // bool
         ThreadsScriptVerif,     // int
         DatabaseCache,          // int
+        SpendZeroConfChange,    // bool
         OptionIDRowCount,
     };