Twisted's BuildBot master configuration

Twisted has a somewhat extensively customized BuildBot master configuration which has evolved over the last ten years. We've kept it private only because it contains some passwords which it would be better not to share, but over the years we have wanted to make it public - because it might serve as a good example to others, because it would let more people hack on it and relieve us of some work, etc. At last this has changed: I spent a couple hours today filtering out the sensitive parts. As a result, you can now take a look at lp:twisted-buildbot-configuration. Add some features! Do some refactoring! Write some unit tests!