Add CSR to certificiates

Add csr column to certificates field, as pending certificates have
exposed the CSR already.  This is required as generating CSR from
existing certificate is will not include SANs due to OpenSSL bug:
https://github.com/openssl/openssl/issues/6481

Change-Id: I9ea86c4f87067ee6d791d77dc1cce8f469cb2a22

lemur/tests/test_certificates.py

@@ -48,7 +48,7 @@ def test_get_certificate_primitives(certificate):
 
     with freeze_time(datetime.date(year=2016, month=10, day=30)):
         primitives = get_certificate_primitives(certificate)
-        assert len(primitives) == 25
+        assert len(primitives) == 26
 
 
 def test_certificate_output_schema(session, certificate, issuer_plugin):