Improve certificate details view, make information more concise (#1021)

The "Description" field can now display multi-line text content.

The "Authority" field now displays the authority name in Lemur (if
known) as well as issuer's name. For imported certs, "Imported" is
displayed.

lemur/static/app/styles/lemur.css

@@ -185,3 +185,6 @@ a {
   text-align:center;
 }
 
+.multiline {
+  white-space: pre-line;
+}