Make startup window modal, other small fixes

src/rpc.h

@@ -59,16 +59,14 @@ public:
     void importTPrivKey(QString addr, bool rescan, const std::function<void(json)>& cb);
 
     void shutdownZcashd();
+    void noConnection();
 
     void getAllPrivKeys(const std::function<void(QList<QPair<QString, QString>>)>);
 
     Turnstile*  getTurnstile()  { return turnstile; }
     Connection* getConnection() { return conn; }
 
-
 private:
-    void noConnection();
-
     void refreshBalances();
 
     void refreshTransactions();