adding find_ungenerated (first commit)

djangoapps/student/management/commands/find_ungenerated.py

+import sys
+
+from django.core.management.base import BaseCommand, CommandError
+from certificates.models import GeneratedCertificate
+import simplejson
+class Command(BaseCommand):
+    def handle(self, *args, **options):
+        l = GeneratedCertificate.objects.filter( download_url = None ).values()
+        sl = [{'user_id':x['user_id'], 'name':x['name']} for x in l]
+        sys.stdout.write(simplejson.dumps(sl))