Use release version description

It seems we don't make much (any?) use of the new version description field. From jira-user:

> The only trouble is that the description does not seem to appear anywhere in
> the UI, except for the ManageVersions page? I think it would be great to
> include the description in each version header of the road map, like this:
>
> +-----
> | 1.0.1 (2004-11.25 | release notes)
> | Performance enhancements and bug fixes
> +-----
> | PROJ-357 FIXED reduced garbage creation
> | PROJ-278 FIXED use sax instead of dom
> | PROJ-176 FIXED you get the idea
> | ...
>