Tidying up Authenticate activity

app/src/main/res/layout/activity_authenticate.xml

@@ -50,7 +50,7 @@
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:layout_weight="1"
-                android:text="@string/cancel" />
+                android:text="@string/back" />
 
             <Button
                 android:id="@+id/OKBtn"

app/src/main/res/values/strings.xml

@@ -325,4 +325,5 @@
     <string name="selectFromOptionselow">"-- select option --"</string>
     <string name="waitingForData">...waiting for data...</string>
     <string name="refreshBtn">Refresh</string>
+    <string name="back">Back</string>
 </resources>