"Non-Product" fixVersion

[Davide Giannella <da...@apache.org>]

Hello team,

while I was cutting the 1.6.0 I attempted a bit of sanitation of our jira.

There are quite a few (677) which are resolved/Closed without any
fixVersion.

https://issues.apache.org/jira/issues/?jql=project%20%3D%20Oak%20and%20fixVersion%20is%20EMPTY%20and%20status%20in%20(resolved%2C%20closed)

Those, by a quick browsing, are all fine as they don't really fix.
They're manly duplicates and cannot reproduce. However it's a bit
unclear as they grow and it's difficult later on to understand if we
missed any fixVersion or was intentional.

I'm for introducing a "non-product" fixVersion that we use to mark all
those issues that are resolved but that didn't make it into a specific
oak release.

Thoughts?

(name of the version can be changed.)

Davide