registration: add support for year of birth

this is only in dav_registration for now. dav_events is following.

dav_registration/templates/dav_registration/emails/inform_self.txt

@@ -22,6 +22,7 @@ Personendaten
 {{ registration.postal_code }} {{ registration.city }}
 Telefon: {{ registration.phone_number }}
 E-Mail: {{ registration.email_address }}
+Jahrgang: {{ registration.year_of_birth }}
 {% if registration.dav_member %}DAV Mitgliedsnummer: {{ registration.dav_number }}{% else %}DAV Mitglied: Nein{% endif %}
 
 Notfall-Kontakt

dav_registration/templates/dav_registration/emails/inform_trainer.txt

@@ -19,6 +19,8 @@ Notfall-Kontakt:
 Erfahrung:
 {% if registration.experience %}{{ registration.experience }}{% else %}-{% endif %}
 
+Jahrgang: {{ registration.year_of_birth }} (ungefähres Alter: {{ registration.approx_age }})
+
 Anmerkung:
 {% if registration.note %}{{ registration.note }}{% else %}-{% endif %}
 

dav_registration/templates/dav_registration/registration_form.html

@@ -90,12 +90,21 @@
         </div>
     </div>
     <div class="row">
+        <div class="col-sm-3">
+            {% bootstrap_field form.year_of_birth %}
+        </div>
         <div class="col-sm-3">
             {% bootstrap_field form.dav_number %}
         </div>
         <div class="col-sm-3">
+            <strong>Nichtmitglieder</strong>
             {% bootstrap_field form.not_dav_member %}
         </div>
+    </div>
+    <div class="row">
+        <div class="col-sm-6">
+            <span class="hidden">Antrag auf reduzierten Teilnehmerbeitrag</span>
+        </div>
         <div class="col-sm-6">
             {% bootstrap_field form.emergency_contact %}
         </div>