[Qt, Trivial] misc minor string changes

- write "Bitcoins" uppercase
- replace secure/insecure for payment requests with
  authenticated/unauthenticated
- change a translatable string for payment request expiry to match another
  existing string to only get ONE resulting string to translate

src/qt/forms/sendcoinsentry.ui

@@ -195,7 +195,7 @@
     </item>
    </layout>
   </widget>
-  <widget class="QFrame" name="SendCoins_InsecurePaymentRequest">
+  <widget class="QFrame" name="SendCoins_UnauthenticatedPaymentRequest">
    <property name="palette">
     <palette>
      <active>
@@ -612,7 +612,7 @@
     </palette>
    </property>
    <property name="toolTip">
-    <string>This is an unverified payment request.</string>
+    <string>This is an unauthenticated payment request.</string>
    </property>
    <property name="autoFillBackground">
     <bool>true</bool>
@@ -700,7 +700,7 @@
     </item>
    </layout>
   </widget>
-  <widget class="QFrame" name="SendCoins_SecurePaymentRequest">
+  <widget class="QFrame" name="SendCoins_AuthenticatedPaymentRequest">
    <property name="palette">
     <palette>
      <active>
@@ -1144,7 +1144,7 @@
     </palette>
    </property>
    <property name="toolTip">
-    <string>This is a verified payment request.</string>
+    <string>This is an authenticated payment request.</string>
    </property>
    <property name="autoFillBackground">
     <bool>true</bool>

src/qt/sendcoinsdialog.cpp

@@ -274,11 +274,11 @@ void SendCoinsDialog::on_sendButton_clicked()
                 recipientElement = tr("%1 to %2").arg(amount, address);
             }
         }
-        else if(!rcp.authenticatedMerchant.isEmpty()) // secure payment request
+        else if(!rcp.authenticatedMerchant.isEmpty()) // authenticated payment request
         {
             recipientElement = tr("%1 to %2").arg(amount, GUIUtil::HtmlEscape(rcp.authenticatedMerchant));
         }
-        else // insecure payment request
+        else // unauthenticated payment request
         {
             recipientElement = tr("%1 to %2").arg(amount, address);
         }

src/qt/sendcoinsentry.cpp

@@ -99,11 +99,11 @@ void SendCoinsEntry::clear()
     ui->messageTextLabel->clear();
     ui->messageTextLabel->hide();
     ui->messageLabel->hide();
-    // clear UI elements for insecure payment request
+    // clear UI elements for unauthenticated payment request
     ui->payTo_is->clear();
     ui->memoTextLabel_is->clear();
     ui->payAmount_is->clear();
-    // clear UI elements for secure payment request
+    // clear UI elements for authenticated payment request
     ui->payTo_s->clear();
     ui->memoTextLabel_s->clear();
     ui->payAmount_s->clear();
@@ -190,21 +190,21 @@ void SendCoinsEntry::setValue(const SendCoinsRecipient &value)
 
     if (recipient.paymentRequest.IsInitialized()) // payment request
     {
-        if (recipient.authenticatedMerchant.isEmpty()) // insecure
+        if (recipient.authenticatedMerchant.isEmpty()) // unauthenticated
         {
             ui->payTo_is->setText(recipient.address);
             ui->memoTextLabel_is->setText(recipient.message);
             ui->payAmount_is->setValue(recipient.amount);
             ui->payAmount_is->setReadOnly(true);
-            setCurrentWidget(ui->SendCoins_InsecurePaymentRequest);
+            setCurrentWidget(ui->SendCoins_UnauthenticatedPaymentRequest);
         }
-        else // secure
+        else // authenticated
         {
             ui->payTo_s->setText(recipient.authenticatedMerchant);
             ui->memoTextLabel_s->setText(recipient.message);
             ui->payAmount_s->setValue(recipient.amount);
             ui->payAmount_s->setReadOnly(true);
-            setCurrentWidget(ui->SendCoins_SecurePaymentRequest);
+            setCurrentWidget(ui->SendCoins_AuthenticatedPaymentRequest);
         }
     }
     else // normal payment