adding better rscore calc from power zone

rowers/forms.py

@@ -991,7 +991,9 @@ class SessionDateShiftForm(forms.Form):
 class DeltaDaysForm(forms.Form):
     deltadays = forms.IntegerField(initial=7, required=False, label='')
 
-
+class PlanByRscoreForm(forms.Form):
+    byrscore = forms.BooleanField(initial=False, required=False, label='plan by rScore')
+    
 class RegistrationForm(UserCreationForm):
     """
     Form for registering a new user account.