Adding gold medal standard to performance chart (optional)

rowers/templates/performancemanager.html

@@ -112,6 +112,11 @@
       on the left. The model balances out after a few weeks of regular training, so don't
       make this chart shorter than a few months.
     </p>
+    <p>
+      Optionally, the chart shows you workouts that represent your best performance for that period.
+      We automatically detect hard workout segments and tests and compare them to world class
+      ("Gold Medal") standards for your gender, weight and age category. 
+    </p>
     <p>
       For this chart to reflect your fitness and freshness, it is important to have all workouts on
       Rowsandall.com. You can automatically import workouts from other fitness platforms. Change