[SRU] LP#1604344 -- changelog: add CVEs as first class citizens

[Andy Whitcroft]

We recently decided that the CVE bugs were not adding any value to the
process.  As such we no longer can guarentee to have a launchpad bug for
a change if it is being applied as part of a CVE.  These will however
have appropriate CVE numbers included.  Promote the CVE number as a
first class citizen when generating the changelog to prevent these
all being mixed together in "Miscellaneous Changes".

Proposing for SRU to all active series.

-apw