Support future compatibility for new timer options

If some future client ever sends us an arbitrary timer value which we do
not currently support, present it as a duration in seconds in timer
update messages and ui, where we would otherwise have rendered nothing,
e.g., "You set the timer to ."

// FREEBIE

js/expiring_messages.js

@@ -32,6 +32,9 @@
         }
         var o = this.findWhere({seconds: seconds});
         if (o) { return o.getName(); }
+        else {
+          return [seconds, 'seconds'].join(' ');
+        }
       },
       getAbbreviated: function(seconds) {
         if (!seconds) {
@@ -39,6 +42,9 @@
         }
         var o = this.findWhere({seconds: seconds});
         if (o) { return o.getAbbreviated(); }
+        else {
+          return [seconds, 's'].join('');
+        }
       }
     }))([
         [ 0,  'seconds'  ],