Make 'Advisory' field opt-in

[raboof]

The 'advisory' field is used when a PMC has its own naming scheme for their advisories, next to CVE.

This field is often misused:

• Isis, Artemis, Feliz, Ofbiz and Zeppelin incorrectly used it by putting Jira ID's in it
• bookkeeper, camel, karaf and ofbiz incorrectly used it by putting URLs in it
• Struts 2 does seems to use it legitimately.

We should probably hide the field to reduce confusion, and only show it for Struts (and any other PMC that asks).

[iamamoose]

ack this approach