Normalise vulnerability data structure

It seems that vulnerabilities can have slightly different structures, presumably depending on their origin. This variability leads to trivial-but-annoying workarounds and bugs.

In particular, the name, message and title fields all seem to have very similar purposes, and may or may not exist on a given vulnerability.

The existence of these fields should be consistent across all vulnerabilities.

This may be redundant, given &634 (closed).