Add an About page

This about page layout is borrowed from K-9 Mail:
https://github.com/k9mail

Italian translations provided by Airon90.
Dutch translations provided by PanderMusubi.

app/src/test/java/protect/card_locker/MainActivityTest.java

@@ -50,10 +50,11 @@ public class MainActivityTest
         assertTrue(menu != null);
 
         // The settings and add button should be present
-        assertEquals(menu.size(), 2);
+        assertEquals(menu.size(), 3);
 
         assertEquals("Add", menu.findItem(R.id.action_add).getTitle().toString());
         assertEquals("Import/Export", menu.findItem(R.id.action_import_export).getTitle().toString());
+        assertEquals("About", menu.findItem(R.id.action_about).getTitle().toString());
     }
 
     @Test