When using HTTP full duplex connections the upstream channel can be idle for
long periods of time and the webserver will time the connection out. Jenkins
sees this and terminates the downstream channel causing the unexpected closure
of the read channel in the CLI client.

Timeout of 15 seconds is based on the 20 second default timeout as seen in
Ubuntu Oneiric Tomcat 6 installations.

property. This releases the HTTP connection in a friendly way and allows the
webserver to recycle the connection a little quicker.

eagerly.

better to define a corresponding descriptor type for backward compatibility and methods like display name.

Add new extension point (class hudson.matrix.MatrixConfigurationSorter) for enbling to sort configurations of matrix job.

It would be better to find out why the nextBuildNumber is at times empty.
In the mean time this will find the appropriate number and write it to the file.

getBuildingUpstream() to public so they can be accessed from plugins,
small refactoring (reuse getTransitiveDownstreamProjects() and
getTransitiveUpstreamProjects() respectively)