global notifications

[jillesvangurp]

After updating the hipchat plugin, all our builds stopped notifying because of some changes in the settings. That is quite annoying since we have a few dozen builds and it is a lot of click work to fix. Instead of having to configure this per job it would be much nicer to have (optional) global notification settings for all builds. Basically, if any build fails, we want to be notified.