make help email configurable as per #5, for now only in data model and form, not surfaced in link

helios/forms.py

@@ -16,6 +16,7 @@ class ElectionForm(forms.Form):
   #use_advanced_audit_features = forms.BooleanField(required=False, initial=True, help_text='disable this only if you want a simple election with reduced security but a simpler user interface')
   #private_p = forms.BooleanField(required=False, initial=False, label="Private?", help_text='a private election is only visible to registered/eligible voters', widget=forms.HiddenInput)
   private_p = forms.BooleanField(required=False, initial=False, label="Private?", help_text='A private election is only visible to registered voters.')
+  help_email = forms.CharField(required=False, initial="", label="Help Email Address", help_text='An email address voters should contact if they need help.')
   
 
 class ElectionTimesForm(forms.Form):

helios/models.py

@@ -130,6 +130,9 @@ class Election(HeliosModel):
   # no longer needed since it's all trustees
   result_proof = JSONField(null=True)
 
+  # help email
+  help_email = models.EmailField(null=True)
+
   @property
   def pretty_type(self):
     return dict(self.ELECTION_TYPES)[self.election_type]