Custom parameter function takes QueueItem

With the change to use QueueItem, the custom parameter function
has lost some context.  Pass a QueueItem instead of a Change in
order to get it back.

Add the parameters to the build object so that they can be used
by URL pattern functions.

Add a NEWS.rst file that lists backwards incompatible changes (of
which this is one).

Change-Id: I526850fb55e25b4b84202820dc3c313d37cbe535
Reviewed-on: https://review.openstack.org/36304
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins