Zaddr fix (#173)

* Use isZAddress instead of hardcoded "z"

* Make last col in Tx table resizable

src/mainwindow.cpp

@@ -181,7 +181,7 @@ void MainWindow::restoreSavedStates() {
     // Explicitly set the tx table resize headers, since some previous values may have made them
     // non-expandable.
     ui->transactionsTable->horizontalHeader()->setSectionResizeMode(3, QHeaderView::Interactive);
-    ui->transactionsTable->horizontalHeader()->setSectionResizeMode(4, QHeaderView::Stretch);
+    ui->transactionsTable->horizontalHeader()->setSectionResizeMode(4, QHeaderView::Interactive);
 }
 
 void MainWindow::doClose() {

src/rpc.cpp

@@ -219,7 +219,7 @@ void RPC::importTPrivKey(QString addr, bool rescan, const std::function<void(jso
 }
 
 void RPC::validateAddress(QString address, const std::function<void(json)>& cb) {
-    QString method = address.startsWith("z") ? "z_validateaddress" : "validateaddress";
+    QString method = Settings::isZAddress(address) ? "z_validateaddress" : "validateaddress";
 
     json payload = {
         {"jsonrpc", "1.0"},