Add more content to the v3.2.0 release notes

Insert additional content and structure to the
Gerrit v3.2.0 release notes. The information is coming
directly from the tickets included in the commit messages
of all changes from the latest v3.1.4 and the current
stable-3.2 branch.

Change-Id: I50fe3a446b1b41715be6a20bf8bfeec1bbf20695
1 file changed