Ugrade Jenkins to 1.509.4

There is an issue with dynamically filled drop down that depends on
another field in the form. If the drop down is nested in the form,
we are supposed to use @RelativePath in addition to the @QueryParameter
but this is not working in 1.480.

Change-Id: Ide59afe293d3dae8171ecd86f75cd38c25583387
Add data structure and UI Support for replication.

The admin can enable replication in server configurations,
add Gerrit slaves, and enable slave selection in jobs.
If the latter is enabled, the user will see a dropdown
containing a list of Gerrit slaves configured with the
Gerrit server that has been selected, and can choose one
slave after which the job will wait for replication events.

Change-Id: Id08852619442290b3b5c8e2f179d10989e98b1af
Implement feature to block build until replication is completed.

Add ReplicationQueueTaskDispatcher that will prevent builds from
leaving the queue until the replication is completed, if replication
is supported and configured for that server. If wait for replication
event times out or if the replication failed, build will be failed.

Add a global configuration parameter to allow configuraiton of
replication cache expiration time.Replication feature requires a
cache for replication events until we can complile against Jenkins
1.520 which introduce a QueueListener extension point.

Change-Id: I58782c2278c1ef68cae405495178c1ea89e279b8