If we are going to hard code the phrase 'Date of birth' let's not har…

…d code it Capital Case.

opal/templates/_helpers/date_of_birth_field.html

@@ -1,11 +1,11 @@
 <div ng-show="editing.demographics.external_system" class="form-group">
-  <label class="control-label {% ifequal style "horizontal" %}col-sm-3{% endifequal %}">Date Of Birth</label>
+  <label class="control-label {% ifequal style "horizontal" %}col-sm-3{% endifequal %}">Date of birth</label>
   <p class="form-control-static col-sm-8">
     [[ {{ model_name }} | displayDate ]]
   </p>
 </div>
 <div ng-class="{'has-error': form.date_of_birth.$invalid}" ng-hide="editing.demographics.external_system" class="form-group">
-  <label class="control-label {% ifequal style "horizontal" %}col-sm-3{% endifequal %}">Date Of Birth</label>
+  <label class="control-label {% ifequal style "horizontal" %}col-sm-3{% endifequal %}">Date of birth</label>
   <div class="{% ifequal style "horizontal" %}col-sm-8{% endifequal %}">
     <div date-of-birth ng-model="{{ model_name }}"></div>
     <span class="help-block" ng-show="form.date_of_birth.$invalid">